If you're into making 2D games, then you should make sure you know about sprite sheets. They are very useful and very important. They also are really easy to make.
What they do is contain all of the sprites for your game (or at least most of them are on one sheet) and they save tons of space. I've been working on a couple of sprite sheets for Unlearn Your Gaming since it's all 2D. The character has already been divided in the game so that it switches views when the right buttons are pressed. The animation is also already in place, which follows the same principle of using the same sheet, but different sections of it.
There's not much else to say. Oh, well you should make sure you line all the sprites up on at least a bottom line. This ensures that the sprites will all be aligned when the are divided into pieces.