One thing I didn't have time to mention is the ongoing debate in the music world over whether or not you should memorize the music that you perform. Some musicians are huge proponents for memorizing music because they believe that it's easier for the performer and audience to get into the music than when there's a music stand literally standing between the performer and audience. Other musicians argue that you can be just as expressive with music and that a really great performer can perform with the same level of connection with their audience with or without a music stand standing between them.
For me, I think a performer should just go with his or her gut. Do you actually perform better without the music? Does memorizing the music allow you get deeper into the music, or are you too distracted by trying to remember what comes next? Do you perform better with the music? Do you feel like you don't need to remember the music and so you get lost in the music more easily?
As you can see, it can really go both ways. It's up to the performer's personality and quirks.
In the end, you need to find out who you are and perform according to how you know you work best.