There is one thing you have to remember when you approach a group of girls - you can’t have them all and you have to pick one that you like the most to isolate.
So that being said, there should really be no difference if it’s a girl or it’s a group of girls. If you don’t feel that way don’t despair. Many guys don’t feel like they can approach a group of girls the same way as they approach a single girl. The problem that actually holds you back from approaching the group is in your own head and your own reality. You are probably thinking it is different because they are already deep into their conversation and they would mind if you interrupted them. Another thing that guys think is that when girls are in a group they are much more secure and it’s much harder to penetrate their defenses but in reality it’s not.
All you will need is the right mind set which is the same one you have when approaching a girl – It’s going to be great, she will be nice, I got nothing to lose, I’m not doing anything wrong, I’ll have fun. That’s the mind set that you should have in order to not feel any approaching anxiety and discomfort.
Another thing that can be useful is a wing-man. If you are determined to get one of the girls (and I only assume you are) you might need someone to entertain the other girls while you make your move and work your charm on the girl you like. It’s also possible to get a girl in a group without wing-man but it’s proven to be a little harder because you will have to spread your attention to all the girls in the group which is a bit overwhelming.
After you’ve learned how to approach a group of girls it’s time to make you next move and that is to isolate the girl that you like.
Isolating the girl you like is the most essential thing that you must do when you want to pick up a girl in a group. Getting her away from her friends so you two can have a little privacy and one on one talk is the most important thing you have to do. This probably sounds impossible to you at first but I’m not saying to take her like across the bar. I’m saying to take her like a couple of steps away she will feel like she is alone with you. All you have to do is take her hand and say that you want to talk to her in a more quieter environment and start walking while you are still holding her hand. If it’s already pretty quiet then say that you want to tell her something important. If you can it would be good even if you are direct about your intentions. Tell her that you want to talk to her alone because you like her best. Don’t do this in the first minute of approaching. Do this after you got to know the girls a little bit so that they’ve earned your trust as a human being and not a maniac so they would approve of her friend to go with you.