I would be interested to find proper materials on this as I have always learned from experience. Justin Miller did just release The Bold Project with Ellusionist and there is a video that comes with it that has Justin talking about audience management and such - However, I haven't had time to watch that video yet so I don't know how good it is. Justin is known for his audience management skills so I hope it's good.
The biggest thing to remember about audience management is that it is your show. Never forget that. Engage your audience, get them liking your show, and lead the whole thing. As long as you're clearly in charge and they are enjoying it, you'll stay in control.
Opening a group will come down to personality, mostly. I open a group by walking up to them and talking to them. I engage them in conversation then steer the conversation to a topic that lets me segue into a trick.
Expect the unexpected. When you're practicing and rehearsing try to think of ways it might go wrong. Then plan for it. In time, the more you perform the more situations you'll encounter where you have to think on your feet, the better you will get at it. Experience really is the best teacher in this case.
