Learn the trick. Understand all of the techniques involved, how it works and why it works.
Practice makes QUALITY, not perfect. You can never perfect a trick by only looking at a mirror, but you can prepare yourself properly.
Find a close friend or family member and practice performing for them. Let them know it will help your confidence.
Work on your patter. Performing a trick without talking or spicing it up, is without question, boring!
Take two weeks off from practicing the trick. When the time has elapsed, discover if you can still perfectly perform with patter present. Say that five times quick...go!
Though you want to have fun while performing, magic is acting like you are surprised as well. When a trick gets boring for you, it is time to perform.