It takes practice. I was fortunate because I actually made myself wait until I was 21 to start drinking. That gave me YEARS of having to turn down alcohol at parties yet STILL end up making more of an impression than the other guys there that were drinking. Here's what I found helps:
1. BE FUNNY.
Like, learn how to tell stories in a funny way, be sarcastic in a way that draws people in, and talk to girls about funny stuff.
2. LEARN TO DANCE.
I never had to drink to have a good time because I'd always get "buzzed" off good music. And - thanks to YEARS of watching Michael Jackson videos - I had a pretty good dance routine, which was a mixture of the typical "dry hump" dancing and ACTUAL dance moves. To this day, I can go to a club and start dancing and have a flock of people cheering me on - including WOMEN who end up wanting to dance with me.
3. COME UP WITH AN AWESOME EXCUSE AS TO WHY YOU'RE NOT DRINKING.
If you're not drinking like everyone else, the questions WILL come. BUT, if you have an awesome excuse, you can turn it into something that helps you get women. For me, I used to do clinical trials in exchange for thousands of dollars. One of the stipulations is that you can't drink alcohol between the time you get accepted and the time you get into the lab for the trial. So, during these times, if women came up to me and asked me why I wasn't drinking, I'd tell them it was because of a trial I was going to do soon. Next thing I know, they're asking me questions, giving me their number and telling me to contact them when I get out the hospital.
Obviously, you may not be doing clinical trials, but it doesn't really matter - women just LOVE hearing stories that are different from everyone else's. If you can come up with a good story that explains why you're not drinking, while at the same time positioning you as someone that's different from the rest, you'll have them eating out of your hand.
Hope this helps!