some people are just too fast.you dont know them for long but they act as if it is so.when you spend some time with them they fell free to make fun of you.things you've heard a hundred times and dont want to hear anymore(at least from someone that has newly entered your life).i wonder if i'm doing the right thing by putting up with them?

Most people are like that - thinking that if they follow the herd with the making fun of, then it will improve the relationship (as you have stuck with it for some time.)

maybe that you should just tell them that it bothers you...if they really care they will stop and bad habits are easier to stop before they become real habits...if that makes sense?

Don't put up with it. Make fun of them back, that's what I would do. I think you need to have some sort of foundation friendship with a person before you start poking fun at them. Anything else is a form of bullying.

What are they making fun of?

If what they're making fun of is something that you can take in good humor and are being friendly about it, then just make fun of them back (in a friendly way).

If they're being friendly about it but the things that they're making fun of are things that you can't take in good humor (I'm not blaming you or anything; nearly everyone has at least SOMETHING that they don't want other people joking about, for whatever reason), just tell them either to try making fun of something else or to stop altogether.

If they're just trying to be mean, just stop hanging out with them.