When you first get your power, don't be ashamed that you're gonna suck at them. You'll constantly make mistakes, and do the wrong things for the right reasons, and the right thing for the wrong ones. But keep trying, and gradually, you'll be able to move mountains instead of molehills. Start small, practice, and grow.

As you practice further, your powers will begin to grow and develop, resulting in more strength behind your power, and possibly even branching out into brand new abilities. You do not decide yourself when your powers will grow, but The Powers do, just like in the show when one of the sisters gets a new power, or a boost! The more you practice and cultivate your powers, the more conceivable it is that you will get better at them. As your character develops, his or her power shall develop with them. It's just a matter of patience, practice, and trusting that when the time is right, growth or development will come.

If your powers do grow or develop, an independant post will be made by The Powers That Be, in the thread you are currently in, stating so, and detailing exactly what has changed. You may be able to telekinetically move people instead of just objects, or have premonitions while you're awake instead of just while asleep, or even gain an entirely new power, but the concepts and details will be explained to you.

Enjoy your powers and remember not to abuse them, or they might do the same to you...