When I give out my number and they don't call back, is it on me?

Yes. The girl doesn't want to seem as if she's desperate to call you and so instead she plays hard to get. She might like you but will not call you. You need to indicate by taking her number and calling her to show that you are interested.

You should have asked her number as well, so that if she won't call you, you can then call her. Most girls hesitates to call a guy that she has just met. You're the guy, you should do the first move.

Either way, don't put all your attention on one person. If she doesn't call and the opportunity to get her number has passed, move on. There are lots of great women to meet.

Maybe some are playing hard to get. Maybe some feel its the guys place to pursue. Get their digits from now on. If you can't maybe you need to work on your approach. If they take your # they are not committed to anything, like if they give a fake #. If they give theirs they have to expect a call. Do they ask for your # or do you just give it out like a business card? You gotta act like you don't care (not being a dick) just like you always have something to do and its no big deal if they don't want to talk again. There will be more girls, after all. Don't come off desperate or too forward/ interested.

Read the book "The Game" by Neil Strauss. It took me a better part of my college career to figure out that kind of stuff on my own. I read it after I was already married because a friend said it was a fun read. But it's the closest thing to a manual on understanding talking to girls I've seen and is close as you'll get to someone actually showing you if you don't have that. I wish I had read it in high school. Don't take it word for word though. Get some ideas on what you're doing wrong or right and make it your own.

Or you could always try to befriend a girl to give you some insight into the mysterious and frightening world of women. It worked for me. Just try to use what you learn for good, not evil. Lol