Fear of approaching people to perform is a form of stage fright, which can affect even the best and most experienced performers. It's nothing to do with how good or well-rehearsed you are. In Derren Brown's Confessions of a Conjuror he recounts how he would procrastinate interminably before introducing himself to a table when he was a restaurant magician. Of course, it can be made easier, and there are ways of practicing the approach.
Here's a plan:
1. Make a list of various types of group. So, this could include a young couple, a small group of older men, a family with children, a large group of older people, etc.
2. Go out on the street and, starting at the top of your list, look for each type of group. Approach each one in turn, get their attention and ask for the time (or directions, or some other small favour).
3. When you're comfortable approaching these various kinds of group, repeat the procedure, except, this time, have a funny line prepared. Along with asking the favour, deliver your line and try and get a laugh.
4. Now, you've effectively learnt to approach various groups and perform for them. So, now you can add in a magic trick. Just one to begin with. Choose a short, strong effect, and, instead of asking for directions, ask if they'd mind watching something you've been practicing.
I think you get the idea. Effectively, you're training yourself to feel comfortable interacting with different types of group, and eliciting a specific response. Hope that helps!
