I learned something interesting about Half-Life 2 while playing Episode One. You may have noticed that the contents of the breakable crates aren't always the same. What I mean is, if you save your game and break a crate, you might get a pack of pistol rounds. Load your save game and break the same crate again and you might get a pack of SMG bullets or a grenade. Well I noticed that if I'm badly wounded, the crates turn into health and armor crates. Once I heal myself up or stock up on armor though, the crates go back to being ammo crates.

So now I came up with a trick for getting full armor. What you should do is, save all the crates until you're hurt. Then go around and break them all without collecting any health or armor. If you do this, you'll be able to stock up on a lot of armor which isn't as easy to find as ammo or health. I'm certainly going to do this from now on.