Can anyone give me some advice about some of the manual penile enlargement techniques? Does jelqing work? Any special ways to do it? Is it bad?

I have never done any of that before, so I can't speak from experience. I can tell you that others have responded to this board and said basically it's a waste of time. One person is even worried that he has damaged his penis through jelquing. The long term effect seems to be neglible, meaning there really is no lengthing of the penis. I wouldn't waste my time or money on such stuff. Be grateful for what you have and learn how to use it so that it pleases your partner. Size really doesn't matter!

Yes, jelqing works but you have to be willing to do it for months. Go here to find out more:
http://pub14.ezboard.com/bpeforums

Have any of you guys actually done it long-term?

Yes, gained an inch. The info on ezboard is free. Go there if you're really interested.

There is no safe and surefire way to extend the length of your penis. Anything you do to try involves a risk, and that is not really an area you want to put at risk. Anyway, as long as you're around average (most guys are... that's why they call it average), you're fine. Most guys are not too small that they even need to worry (if you are under 3.5", maybe then), even though they always do, just like women worry about their weight.