here's the deal bro, if a girl is checking you out or you are checking out a girl she will smile or something that lets you know to come over and initiate conversation - pretty much just flirting (if you know thats how it works, nearly every girl is following these rules - at least sluts at the bar - and if you understand how they expect it to go down you can get chicks into bed pretty fast, you can't be scared to make a move though) from their you initiate contact and flirt. So its more of a mutual hitting on each other. I definately initiate once I get the go ahead so I would say as far as your question goes I hit on her 100%.
(just a brief note, don't get heavy on the relationship type ish with these types of girls - ONS or even friends with benefits - or you'll blow it for sure - this is strictly to get laid)
alcohol probably 50% of the time (i like to go to the bars), i don't get laid all the time - maybe once or twice a month - with no dates, no flowers, nothing - just remember they want to fvck just as bad as you - NIKE style - just do it.