Just be nice to people. Consideration for others and others' feelings is a good place to start. But it's important to be yourself too (but if you're being a jerk you might have to make some adjustment. lol)
It'll be a lot easier if you can find people who share common interests as you - you'll have a lot more to talk about and it'll be easier to get to know them better. Of course people from all different kinds of places and interests can be fun to meet, so be open to the possibilities.
And remember you don't have to be everybody's best friend.
You might just not be used to conversing or socializing very much with people. Conversation is really important, and if you keep silent a lot of the time even if you mean well, people won't approach you since they might think you don't like them or want to be left alone. So if people don't come up to you, go up to them and start up some conversation. If you're not used to it it might be awkward, but you'll get better at it the more you do it.
Also make sure to smile. It usually helps lighten up the mood. :)
Those are really just tips on how to get to know people.
It really depends on whether or not you prefer having a large circle of friends to hang out with, or prefer having just a few good friends. That's something you have to figure out for yourself.
And just for the record, the people that made fun of you for not knowing how to make friends - they're not worth bothering with, let alone making friends with. So don't worry about them.
Make friends because you want to, not because people make you feel bad about not having any.
Oh yes and whatever you do - don't let people make you feel bad for being "school smart." Honestly that should be something you should be proud of. I'm sure you'll be better off with people who understand that academics are important, and are willing to support you in your academic pursuits.
Sorry for that long post lol. But hope it helped. :)
Best of luck!