If a woman fancies you she'll let you know - stuff all this going over and talking to them - there's more important things to do when you're on a night out - like drinking!
If she doesn't come over or 'bump' into you - she's obviously not that interested.
The age thing is actually quite relevant too - most lasses under the age of 25 don't usually have the confidence to approach a stranger.
So for a lass to come over to you - you must
a) not look desperate - chatting to a few other lasses that you know will ensure you don't come accross as a billy-no-mates psycho and give her a chance to chat to one of them in the toilets to find out your situation.
b)wear clothes you like and feel comfortable in - it shows who you are - lots of designer labels does not maketh the man - if you like a big woolly sweater and feel comfortable in it then wear it.
c)do not hold on to the scenery - you are meant to be fun, confident and considerate - not a combination that's acheivable when hanging drunk.
d)do not stand in a huddle with all your mates around you - it's intimidating
After that - the washing, intelligence, witty repartee, not staring at her tits etc come in to play in varying degrees depending on how mush alcohol she's consumed.
