Well, i've never asked a guy for his phone number XD but i have been asked mine on occasion.
One time was when i went to a bar with my medschool gal friends (i usually don't go out, but i was dying with boredom at our dormitory then XD).
So i went out with them for some dancing and drinks (i was spiritually dwindling at the time, not proud of it.)
As i was just dancing and having fun, a guy starts dancing really close to me, then hands me a piece of tissue, asking me for my number.
Apparently he's been sent by someone who's interested in me, and kept on bragging that said guy was someone who works with the media and at a TV station.
Of course, i was flattered as heck, but i didn't give him my real number XD one of my gal friends said she'll right down her boyfriend's number there instead (with said boyfriend being there with us, giving his thumbs up XD).
The other guy who my friends brought along asked for my number too. Since we danced a little, and since he was a friend of my friend, i gave my number, just as not to be rude or offending. He texted me at once that night and the following day. I think he got a little smitten, and was hoping i'd be sweet right back at him, but i kept a friendly, non-commital stance, which he expressed his dislike for. And i never heard from him again XD
I'm not the type who likes to lead anyone on. "No" means "No", no matter how many times i'm asked.
But if i'm considering saying yes, i just...
give that "maybe" look.