okay, here is what I do on a night out. sometimes it works, sometimes it doesn't, but important, it *sometimes* does, as opposed to "never".
1) choose the club wisely. if you're a sporty guy/lad, go to a "normal" club. if you're alt. then go to an indie club. you'll meet more compatible people
2) arrive semi-smashed - you'll be happier (more positive vibes) and you'll be more social/willing to approach everybody. and when I say "everyone", I mean both guys and girls. chances are, the guys you meet will have female friends. even if you feel stupid doing it, people love it when people talk to them. I mean, don't you appreciate it when somebody starts a conversation with you? I know I do. you just need to pick the right thing to say. it will always be good to be remembered as that crazy outgoing guy who was confident and funny. complimenting everybody in a particular way (guys *and* girls) also goes a long way because people love being complimented.
3) it never hurts to take a minute to go outside for a cigarette even if you're not a smoker - a lot of people will be outside and it's a good way to meet people or re-meet people you already saw inside the club
4) hang out with your friends and meet people co-operatively. you'll want to give off friendly vibes like that. if you meet a girl (or guy), introduce them to your people and get everybody acquainted. meet the people your riends met, and then meet *their* friends. again, like I said, it's a good thing to do this, not creepy. it's only creepy if you're awkward and forceful. if you're drunk, it will flow naturally.
5) never buy a girl a drink. honestly, just don't. it won't help you. its just a rip off and will make you seem desperate.
6) have an after party and invite everybody along. this probably works better for me because I live very close to the clubs in my area, but telling people that you're having a beer pong/mario party 5 minutes down the road is a great opportunity to bring girls home. I have a very impressive and large student house with a bar in the garden, statutes everywhere, fancy furniture etc so if you've got that setting use it.
7) did I mention look good? yeah. look good. smell good. be clean. have good breath. have good clothes. you don't have to look gorgeous. just look your absolute best.
8) be good at talking to people in general - practice it and see what works. laugh a lot. poke your tongue out here and there. smile all the time. break touch barriers.
oh yeah, don't forget to actually hit on the girls. forgot about that part.