Know your role 

When you accept that the night won't be about you, you instantly become a better wingman. If you're there to assist, you need to lay low like Stockton and don't try to score, so that your boy will be practically guaranteed to (like Malone). 

Why? Because a woman knows when a man is in pursuit. That's why the best wingmen are taken, wifed up, or at least held down by something semi-permanent. A man who already has a woman (or is resigned to not looking for one) can successfully approach a group of women, but if she thinks you're selling something, you've lost.

Instead, work the true wingman angle by shelving your ego and being all about your boy. Go in like you have nothing to lose (because you don't! You have nothing at stake.) and you'll appear nonchalant and confident—just like a taken guy—instantly lowering their guard (and raising their interest).