Society has screwed guys over with its set rules - guys do the chasing. Girls certainly do go out looking to get laid at the end of the night, however they expect it to come to them, as society dictates.
Most girls don't approach guys - that's what the game is about. You've got to break into the sets, work the friends, seem interesting and work from there. Sitting back and hoping someone jumps at you isn't going to happen - but if you make an active approach you'll find things can happen quite quickly.
Take last night for example - I zoned in on a girl with her friend. After around 20 minutes I knew I was in there - a while later she left her friend and brought me home. She was just talking to her friend, not looking around for anything - but I broke into the set, got chatting with her, and she was definitely just looking someone to take home - which I wasn't complaining about!
