Warnings, or, "The Reality Check"
These places *are* full of gay men. A signifcant percentage *are* there with hopes of picking up. Anyone going to these bars for the first time *will* be recognised as "fresh meat", and (especially if they're young) *will* attract attention. This can be anything from eye contact acroos the bar, to a quick grope as someone pushes past in a crowd, through to the occasional persistent pest who just won't leave you alone.
My advice would be: Don't be suprised by this. Do take the attention as a compliment - but if someone is pushing too far, make it clear to them that their actions aren't welcome. If they persist, draw other peoples attention to whats going on - tell your friends first, tell other people around you.. accidentally spill your drink on someone, thus drawing attention - most creeps will vanish under even the slightest scrutiny.
Do watch your drink. Drink spiking does happen.
That said... I've never had a problem worse than someone brushing past a bit closer than they needed too, or persistently trying to get my attention. I don't know anyone who's had their drink spiked deliberately - although one of my friends did once grab another friends drink by mistake and imbibe rather more than he intended..
If anything, I've caused more problems than I've experienced. There was the time I spotted someone I'd been dancing with, walked up behind him, removed his jacket - then noticed his t-shirt had changed colour and realised this was a completely different person.
There was the time I reached behind me to grope a friends arse, and got another random guys arse instead - this time, it was the unexpected largeness and softness of the arse that tipped me off.
There was the time I grabbed someone I was talking to and pulled them into a quieter corner - only to turn around and realise I'd grabbed the wrong hand and pulled the wrong guy after me.
Moral: Don't do as I do. Watch who you're grabbing in a crowd..