Protection of your water craft, tube, pontoon, etc from damage while on the water
  Backup maintenance while off the water
  Launching and leaving the water without upset
  Weather, water currents, wind - dealing with difficult conditions
  Personal Safety: Eyes from hooks & sharp objects, exposure to sun, wet, cold, fitness to tube
  Other large or fast water craft driven dangerously close and collision avoidance
  Situation recovery in the event of ending up in the water for whatever reason

It is our responsibility to ourselves, and to other water users,  to take care of these BEFORE we go on the water.

Some of these issues apply to all small craft, some are specific to the float tube.

Launching and exiting:  Place donut tubes on the ground at the waters edge, with the fins placed under the tube seat in the "working" position. Next step into the tube. Slip your feet into the fins, one at a time, and sit on the backrest while you pull on the fin heel straps. Pick the tube up by the handles with you inside and walk backwards out into 18" of water, sit down, clip up the crotch strap and paddle away, clipping up the stripping apron as you go.
If you have a Vee Tube life is simpler. Put on your fins at the water's edge, with the tube beside you to rest against. Place the tube floating on the water in the 4"- 6" deep area, reverse into the water with your fins on and push it out in front of you.
When you get to 18" of water sit down and close the bar, if it has one.  Velcro up the stripping apron so you can't drop any tackle in and paddle out.
To get out, fin gently into the shallows, stand up and walk backwards out of the water. Sit down and remove your fins. Then step out of the round tube or open the vee tube and walk out.
Avoid muddy launching sites ( mud traps the fins, and you can trip up ) and sharp rocky launch sites ( scrapes the underside of your tube, and you might push it down onto a sharp edge with your full weight while getting in and out). Unsuitable launch sites cause wear and tear on your craft during the launch or exit from the water. What you want is a nice compacted gravel or sand beach.

When dithering about prior to launching, if you let go of it, a wind from the shore can easily blow your craft out onto the water over deep water. This leaves you embarrassed and stuck on the lakeshore looking helplessly at it, and having either to ask a friend to go get it, or else walk around the lake to retrieve it where it blows ashore.

Personal Floatation Device: Wear your life jacket all the time. If it is uncomfortable to wear all the time, buy a better one. Do not plan on putting it on when you need it. ( Would you try putting on your seatbelt during a car accident? )
Automatic inflatable jackets are prone to going off in the back of the car on the way home due to dampness, so a manual pull-cord jacket is preferable.
I currently use a buoyancy aid fishing jacket which also doubles as a padded insulating waistcoat. A buoyancy aid gives lift, but does not guarantee to keep you upright with face above water, and has no crotch strap to prevent a possible wriggle out. So a life jacket is safer than a buoyancy aid jacket.
Don't economise with a cheap jacket, your life is worth more than any cost saving, when the day arrives that the unexpected happens to you.
Waders: Neoprenes are warm against exposure, and add extra buoyancy, two desirable qualities - so they should be regarded as the standard. Thinwall lightweight breathables can serve as a special use alternative for summer when neoprenes become too heavy and warm.

In spring and autumn be aware of the fact that exposure is dangerous. If you get wet will you be warm? Wool and fleece stay warm, whether they are wet or dry. Neoprene is also warm, but many other materials while warm when dry are useless if they get wet. A down jacket is an example. These materials are not suitable as tubing clothing.

The tube is a a stillwater design: So use it on lakes. Your water speed is too slow for safe manoeuvring on fast rivers, so you can be carried under overhanging bushes against your wishes. And you have parts of you sticking out underwater positioned to strike against a rock or snag as you drift with a current. So stay out of rivers in float tubes.
The pontoon design is much better suited to flowing water since a pontoon's water speed is quicker, and nothing projects out below. There are some pontoons specially made for river use. Also, the problem with pontoons, wind, is not really present on rivers which tend to be more sheltered from the breeze.

Inflation Air Pressure: A float tube bladder should be inflated enough to make the wrinkles in the cover material disappear, no more. When inflated to 3 - 4 psi, the tube is very firm, not rock hard. Try to not over inflate your tube. This shortens it's life by stretching the stitching, or maybe you could even burst a seam.
Don't leave a full float tube in the vehicle in summer sunshine. The heat will cause the air inside the tube air bladder to expand and thereby over inflate your tube, possibly damaging it. In this situation let some air out so the tube is only partially inflated, squishy and wobbly. No harm can come from the heat then.

Backup Floatation Chambers in the Tube: If your tube has one main air bladder, make sure to have another air chamber in the backrest. This means that when the life jacket is included, you have three systems of floatation. My current tube has a single main bladder, and I am not happy with that, so I have the backrest bladder, and also another smaller backrest bladder in the storage pocket above the backrest, and my jacket. With 4 systems I'm not going to sink, but I also don't plan to lose any rods or gear due to a loss of buoyancy. If you have a single chamber tube with no backrest space (!) lace an air cushion to the seat and sit on that. And once again always wear your life jacket!

Don't kick off a fin and lose it: Tie your fins to your ankles with fin savers. This is a big hassle avoider. Fins can work loose and come off, or get trapped in bankside mud and be sucked-pulled off just when it's a real pain to have to fix them, Pay attention to if a fin works loose, and simply reach down and adjust it, rather than kicking it off and losing half your speed. This is far easier to do in vee tubes compared with round tubes.

Wear a Hat: It is always possible to have a hook hit your exposed head while fishing, and false casting flies in a gusty wind is a great way to make it happen. So a hat is necessary.
Also when you are sitting low down near the water surface, the reflected ultraviolet rays is added to the rays from overhead and this "double dose" can cause severe sunburn. A peaked hat blocks the UV from the sky, giving face protection, but leaving the reflected UV from the water bringing you back to normal sunlight exposure levels.  A peaked cap shades the face but a full brimmed hat protects the face, and also ears and upper neck and is better.
So buy a hat with a shady brim, reduced backlight on the lenses reduces the need for "side screen added" type polarized glasses.

Wear Polarized Sunglasses: With hooks flying around your head, some kind of eye protection is desirable.
There is also the fact that light reflected off the water prevents you seeing into the water, where the fish are. The glare can be eliminated by wearing polarized glasses, which will also give eye protection from hooks etc.
Remember that a polarized lens is not a tinted lens. They are very different. A tinted sunglass reduces the light going through by a fixed percentage. So you get 80% or 70% reduction or dimming. Unfortunately with simple tinted lenses, good light and glare pass through to your eyes in the same proportion they arrive at the lens.
On the other hand, a polarized lens removes a great percentage of the glare, the light reflected off the water, and leaves most of the light from above. So the sky stays the same. However the reflected sky on the water surface darkens. This allows you to see into the water better. For this reason every angler worth the name should wear polarized glasses as long as enough light is present to make them viable, taking them off only during dark rain showers, and in the evening at dusk. Sight fishing for cruising fish is almost impossible without them.
Try to prevent light getting in at the back of the lenses, because it will reflect into your eyes. The ideal situation is no light at all coming in at the side, and rear, so the lens surface nearest your eye is darkened, with all the illumination on the outside. Remember how easy it is to see into a lit up aquarium from a dark room, compared with looking into the sea from a brightly lit beach.
Some glasses have polarized side panels to reduce back-glare and these are good with a peaked baseball cap. Better still, you wear a fully brimmed hat instead. This blocks backlight better and this goes a long way to produce the best underwater vision.

Tubing in saltwater falls under full coastguard regulations, and in some places (eg harbours) the law requires that a visual indicator over a certain height must be shown. The normal answer is to fly a pennant on a flagpole. Fit a metre long rod-rest, or old rod tip with a brightly coloured pennant tied on at the top fluttering in the breeze.

What about fishing after dark? Pennants and patches do not work in the night. Get clip-on cyclists flashing LED light units! The boating rule is red on the left (port side, green on the right (starboard) side, white in the middle on a raised pole. Remember left and right are calculated as if you are in a boat, moving forwards, and the tube moves rearwards. So the white is easy, but the red goes beside your right hand as you sit in the tube!  Clip them onto the D rings each side of your tube and you stand out once more no matter how dark it is.
Once again if there is a boat navigation route - it's preferable to stay out of it after dark, even if you do carry lights. Not every boat owner is looking out as hard as they should be, especially after they think they are safely away from shore and it's rocks, and you are quite low in the water.

Sonic Communication on the Water: The problem of bad visibility on the water for ships was solved long ago, long before radar was discovered. Fog horns are sounded periodically by ships, so if you can't see them, you can hear them!  If a specific location requires that my tube must cross the "boat road" I sometimes carry an air-horn in the soft drinks holder of the tube. It can be sounded without even having to pick it up by triggering it where it is .
It's a good idea to carry a whistle clipped to your PFD. Some are supplied with them. If you get into difficulties you can attract the attention of other water users. Having it attached to the life jacket means that even if you leave the tube you can still use the whistle.

Right of Way on Water: It doesn't matter if you have right of way. Wait till they pass, give way, always allow more space than seems necessary. Boats are bigger and faster! Stay out of their way and don't put yourself into a situation where a careless boater can cause hurt to you and your craft.
Jet skis are not compatible with safe tubing. Their operators do not look enough where they are going. It is unwise to tube where jet skis go. If you really must go to such a water to fish, go at dawn and arrange things so that you are leaving the water as they arrive. The disturbance they make puts fish off feeding anyway, so you will not miss any worthwhile catch from your early departure.

Mini First Aid Kit:  A mini first aid kit remains in the tube. I have mine in a plastic self-seal bag in a small box designed to hold a bar of soap while camping. When it's necessary, maybe a cut from a hook point or a pike tooth, I'm glad to have it. Those cold wet skin cuts bleed a ridiculous amount!

Better First Aid Kit:  A better more complete first aid kit remains in the vehicle. I have mine in an airtight lunchbox to keep it airtight. The only things I use much are paracetemol when fishing while I'm not quite well, anti histamines when irritated by big pollen counts, and the occasional sticky bandage for a small cut. However, over the years I have opened it several times for friends and other anglers nearby who were unprepared, then got a small injury, and had no first aid kit themselves.

Extreme Weather: Get the weather forecast the day before, the night before, and the morning of your trip. Learn how much breeze you are physically able to paddle in and stay within your capabilities. Learn how your local water differs from the general region forecast due to local features .. more wind, less wind, tendency for still morning and evenings, and so on.  Launch at the downwind shore, and fin upwind, then the wind carries you home. Be aware that a strong wind gets the top layer of a lake flowing in a downwind direction, so you may have to fin against the wind, and the water flow if you get into the wrong position, and this can be exhausting. Avoid the problem before it becomes a problem, by going to smaller lakes on windier days.
Don't go out on the water waving a carbon fishing rod/lightning conductor if there is an electrical storm possibility.

All other things being equal, risk is directly related to distance from the shore:  Say you want to fish the far side of the lake. It is safer to drive around, than it is to fin a long journey across.  It is safer to fin round the shallows, where the fish usually are, than it is to cross the middle. Safety is dry land when you are in a water craft. Unnecessarily high distance from dry land is the same as long time delay from dry land ... it is a higher risk. Always choose the lower risk approach to water sports , if you have a choice.

Float tube repair kit:  I never leave home without it. Basically it's a simple bicycle repair kit with a couple of extras. The plastic bag contains tube patches and glue, and also wader repair materials. It remains in my car, but I allow for the possibility of sticking a hook and making a pinhole while out on the water. For this purpose I carry  polyurethane tape which can make an instant fix to an air bladder if punctured.
A pinhole is nothing to be alarmed about, you hear the hiss, or see a stream of pinhole bubbles rising where they should not be. It will take a very long time to deflate in such a situation. Just paddle towards shore, and decide while en-route whether an on the water fix is handier. Most of the time you want to get back to the car to do a proper job, just so as you won't have to do it again later, if you do a temporary one now.
The handiest glue for seams, or valve edges is sold as Aquasure, Aquaseal, neoprene diving suit glue, or the glue for polyurethane gutters.

Fishing hooks and knives:  Should be stored in rigid lure boxes. If you leave them in the tube pockets loose, sooner or later you will lean on that pocket for support, maybe just shifting position for comfort, and push a hook point into the tube for a pinhole leak. So use the lure boxes and keep your ship tidy.

When fishing for bass, mullet, perch:  Pay attention so that the spiny fin does not put a pin hole in your nice tube. Play the fish out at distance, then bring it in close. Don't drag it in fresh, and then have it hopping all over you and your tube while you try to grab it.