You wake up one night and there's water up to your ears. The ship's at a funny angle. There are alarms going off everywhere. People are screaming. You get out of your cabin but the next few minutes are a blur until you find yourself cold, wet and in an inflatable liferaft with a few other random people not knowing what to do...
Right, let's keep things simple, you're not trained in this sort of thing, but there's no crew with you and someone has to take charge. So if you remember nothing else, remember this; CUT, STREAM, CLOSE, MAINTAIN.
CUT; this means cut the painter. The painter is the line (or rope if you prefer) that's got you attached to the rapidly sinking ship. There's a knife kept next to painter in the liferaft. It doesn't have a sharp point so that you can't puncture the inflatable raft. Gather in as much of the line as you can before you cut it, this might come in useful.
The painter should be attached to a hydrostatic release on the ship that will automatically cut the line when the ship is about 4m underwater, but occasionally they don't work, or the line gets tangled up in debris, that's why you might need to cut it.
STREAM: in the liferaft somewhere are paddles and something that looks like a windsock, called a sea-drogue or sea-anchor. Use the paddles. Use the sea-anchor by throwing it away from you and pulling on it. Get away from the side of the ship. You can lose buoyancy and get dragged down or else get pierced by a piece of flotsam. A bit of clearance will also give you time to think. If it's rough the sea-anchor will also help to keep you stable, or if not it will stop you drifting too far from the wreck site. That's essentially what 'streaming' is, so USE IT!
CLOSE; nobody will survive very long if they're exposed to the elements for a lengthy period. Close the hatches. It'll keep the heat in. You can open them again later if it's too hot.
MAINTAIN; this is where the surviving comes in. People have survived for 3 months+ in inflatable liferafts. People have also died within hours because they didn't know what to do. Written on the deckhead (roof) of the raft is a list of preliminary instructions. Once again FOLLOW THEM! There are a whole load of things that you can do to keep yourself alive;
Even if you've never been seasick in your life take the pills, dehydration rates will increase if you're chucking up everywhere, and it will help to keep an already difficult situation a little less unpleasant. If it's cold then bail out the water and inflate the floor. Huddle together for warmth and pay particular attention to any injured members you have. Set watches and give people tasks and responsibilities to keep them occupied and their minds off the situation. Morale and the will to live can be more important than anything else.
You obviously want to be looking out for rescuers but you also want to find other survivors, several rafts strung together make a bigger target than a single one and more rafts means more water, food and other essentials.
In your survival pack there will also be a book called 'Handbook for Survivors', this will give you a whole load of information on keeping yourself alive, as well as giving you something to read whilst you await rescue (unless somebody brought the new Harry Potter with them and managed to keep it dry).
This is the modern world, even if help isn't at the scene within a couple of minutes it will be there in hours or days. Any half-decent crew will have gotten off a Mayday by several means. Use your resources. You can survive without water for 3 days and food for 30 days. Help will be on its way, just remember that nobody is a survivor until they're back on dry land and you'll be fine.