They turn out best with light behind the subject. You can further enchance a silhouette to being more dramatic by playing around with the contrast, for example.
doesnt anyone know how people make those really nice looking silhouettes?
i'd like to make my own w/ pictures but have no idea how they do it
sry, i dont have any examples
If you are shooting against a bright sky, like a sunset, expose for the sky and you will get silhouettes in the foreground. If you expose for your subject, your sky will be off.
To add to what JRalston said ... if shooting a sunset, take your meter reading off of the sunset (not the sky surrounding it). In other words, meter the part of the sky that you want to turn out the best. The rest can be under or over exposed as you desire, but you'll want to keep the color.
After you do that, the exposure will be set to such a brief period that anything position in front of the sunset will become a silhouette.