Here's an unpleasant thought; what are the rules for drinking your own urine? Some apparently do this for fun, but what about for survival situations?

If you're able to find enough edible plants (via watching other animals), it might also be worth trying to cultivate them, but this depends on your broader circumstances.

Don't expect to stave off dehydration by drinking urine. Your body expels salts (and other substances) through urine. Thus you'll die from hypernatremia drinking urine or seawater, just as happens if you don't drink water at all.

Apparently blood and alcohol are also bad. They are processed as food, which requires large amounts of water from your body. Thus while they're both fluids, they result in a net loss of water.

Fish apparently have a column of fresh water near their spine. You can cut them open and drink from this. You can also suck fresh water from their eyes.

Edit: Oh, hey, a citation:

http://en.wikipedia.org/wiki/Urophagia#Attempting_survival

Everything else is from "Complete Survival Manual," Michael Sweeney.

Depending on climate either shelter or water is the most urgent. Most people can go weeks to months without food if they must.

If you find yourself behind enemy lines, you need ammo, especially if they are hunting you down. Otherwise keep it for emergencies.