If you've never wore waders, then, I would seriously suggest that you prepare both mentally and physically to respond calmly in the worst-case scenario. All the advice in the world is not going to prepare you for when it happens for real. Only experience and practice will help.
If you've never wore waders, then, I would seriously suggest Two suggestions you can do to better prepare yourself for the worst, is to put a pair of waders on and walk into a swimming pool or if you don't have a swimming pool, go out to a river (during a warm summer month) with a friend and purposely fill your waders with water and float down the river for a short while so you will experience the feeling of the water rushing down and filling your waders and practice the motions of floating on your back, paddling with your arms to keep your head up, using your feet to deflect yourself over boulders, and wait until a suitable exit point presents itself. This will help prepare you in advance to deal with a panic situation in more colder waters when the fishing is more plenty. In turn, being more prepared, you should feel more confident about venturing out in the river to catch that great fish of the day.
Know your limits:
1. Use a Wader Belt - it just may save your life!
2. Do Not Panic - this is the worst thing you can do and what causes the most fatalities!
3. Wade Up to Only Your Hips - (water rise fast and waves can overpower you).
4. Waders Do Fill Up With Water - make sure your wader belt is securely fastened around your waist in efforts to slow down the amount of water that will enter your waders in case you slip and fall into the water. I have discovered that there are types of breathable waders will suck to your body when wading through water, which is good, because if you do fall, it will take longer for water to fill up in them and will allow you more time to get to safety.
5. Wear a Personal Floatation Device (PDF) if possible
6. Read the Water - know your surroundings, beware of slippery rocks.
7. If Wading in Rivers, speed and pressure per square inch is multiplied tremendously in certain sections:
a) pinched water with a turn or When wading heavy water, interlock arms with another fisher, it looks odd, but two people become very powerful when they have each other to catch the stumbles.
d) Wading staffs are a valuable asset, even if you need to leave them at the crossing.
e) The fishing generally isn't better on the other side, it just seems that way.
8. Test the Waders for an Emergency Situation. - "If you have never experienced what it is like to have your waders fill with water, I would seriously suggest that you put them on and walk into a swimming pool. All the advice in the world is not going to prepare you for when it happens for real. Only experience and practice will help."