Depends on what your team and or coach wants you to do. Generally, you need to be in the slot. Whether or not you go into corners and behind the net is something you need to discuss with your Dmen and coach, they'll have opinions and ways they like to play.
Cute Hockey Bunny's diagram is a good starting point.
It's also going to vary based on your speed and strength. If you're not strong on the puck, don't go into corners. If you're not fast, don't come low behind the net. You need to be part of the rush too.