I know what you mean, what tends to work for me is to just smile when you get eye contact and don't break it, I will often try and gain someone's attention before looking at them then it's you catching them looking over. Then I wont break it too suddenly and maybe point at them and gesture them to come over.. Usually it will make them a little embarrised but I find people tend to come over or start some kind of interaction. If they do it will appear to everyone in the club she hit on you. Monkey see, monkey do.

It's a very fun and playful way to open an interaction whist avoiding canned crap. Likelihood is, if she's keeping eye contact with random guys she's into it and looking for it.. You have less picking and choosing but at least you avoid some bitch messing up your state from the get go and spoiling a good night. I'll start talking to 'random' ones once I'm pumped enough, sometimes this really helps to start my night.