I prefer to do the approaching but let them ask for my number or whatever. If they approach me I need them to let me put my hat in the ring to be interested. I tend to clam up a little if a guy comes over and starts giving me the hard shell even if I think he's attractive and like his personality.
It is just too much for me to take in at one time. Men believe it or not women aren't always just waiting around with the intent of being approached. I know most men don't think this but if I'm at a bar more times than not I'm there to drink.
I guess what I'm saying is I need a second to catch up is all. Approach, heavy charm, what's your number strung together will overwhelm me.
Unless the guy is a douche I'm polite and friendly whether interested or not but I do make it obvious if I am but if he's all go with us to this next bar within the first five minutes then he'll get a no.
When it comes to asking girls out its not that i was scared i just didn't want a relationship. I've been asked out a few times by girls and they got sick of me pretty quick lol but my longest relationship lasted 2 years.