One did you do with a 1 set to get started. Practice. So what do you think you need to do with a 2-3 set?
Try being flattering and nice/pleasant to the friend - I spoke to one 2-set by telling one of them was gorgeous, but I told her friend that she was very beautiful too (which btw she was quite pretty). She just stood back, but I was polite and paid some attention to her, bantered with her a little as well. She didn't really try and drag her friend away - worst it came to was "We're going to be late for a class!", but she was patient while me and her friend took down numbers.
I'm not suggesting they'll all be like this, but acknowledge the friend a bit too, even if you're going direct on the target, which I believe is still possible in a group situation.