Alternate picking is what you probably are doing now. You just pick the string normally. There's also finger picking, where you take your fingers and play w/ out a pick, duh. Then theres economy/ sweep picking. This is more complicated and is used to play arpeggios. It makes it easier to play arpeggios than using alternate picking, it is used alot is shredding. There are some lessons on that here. There are other style of picking but I cant remember off-hand.