If they aren't your friends and have never shown interest in you before, or if they haven't been an acquaintance type friend who you talk to in passing or occasionally make small talk with, I wouldn't help them for free. I would charge them for my time tutoring them. If you are getting a lot of in class, or studyhall etc type questions of "Hey, how do you do this problem?" I'd tell them "Not right now, I'm in the middle of something" If you want to help them, then charge them money for your tutoring time, or have them trade out in some way like teaching you a skill they know, etc.
If the ones asking you are jackasses to you or others, the rest of the time, then I would tutor them for free but teach them the wrong way.
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I'm giving it another shot. We will see.
My forum is still there and everyone is welcome to come join as well. There is a private women only subforum there if anyone is interested. Also, there is no CAPTCHA.

The link to the forum is
http://www.rightplanet.proboards.com