Penmanship is a virtue.
if it's spelled wrong, it's probably fake.;)
Autopens are easy to spot. If your autograph looks exactly like somebody else's autograph, it was signed by a machine. If they're slightly different, they were signed by humans.By the way, most of the "experts" don't have the training or the references to accurately spot fakes all the time, either.
I try to check around the web and see if I can find any other versions of an auto. If I find a few dozen or so that look the same and mine is different, well there you go. Otherwise, I would just go to Gellman for help.
I agree with dogfacegremlin. I would check as many different examples, especially certified copies, as you can for comparison. But as Paul said, you don't want them all to look exactly the same.