Heh, cool, I'm a guru
! Never knew about that one.
Tony's trigger info is already very good, so I'm just going to add in some extra little things to do to make it even faster and lighter.
Making Your Pull Lighter
Well, I believe Tony already mentioned the orthodontics rubber band as a replacement for the sear spring trick, so I won't talk about that. However, if you do do that, you might want to think about putting two rubber bands together. This way, if one somehow snaps (unlikely, but possible), your gun won't go full-auto on you and you won't have to take it apart to fix it. Okay, now that you've done that, your pull is already going to be substantially lighter. If you really want to add to that, do the old pen spring trick. *Note: this will take a few hours to do* Find a clicky pen with a wide spring (preferably, doesn't really matter). Take the spring out, and find something HEAVY (I used a paper weight that says "Lead, Follow, or Get the Hell Outta the Way", heh). Put the spring down on a flat surface, and put the heavy object on top, compressing down the coils. Wait about 4 hours, come back, and your spring should be smaller than the original. Now, snip it with wire cutters, pliers, whatever, so that there is about a half-centimeter of space between the notch in the trigger where the spring goes and the top of the spring. This should make the pull much lighter when coupled with the sear spring trick.
Making Your Pull Shorter/Snappier
Alright, there are a few things to do for this. You can make a trigger stop, but it will look crude and won't do anything but be ugly. For a very easy mod, simply take out your safety. The safety, I find, rubs against the trigger, so taking it out makes your pull faster. I recommend you get a barrel condom if you do this. Another good idea is to take out the trigger spring completely. This will make for a slightly faster ROF, and it's obviously very easy to do. To make your pull shorter, do the same thing you did in tony's mod with the tape on the pin, only add it to the pin that the the biggest hole on the trigger goes on as well. A good thing to make your pull shorter and a bit snappier is to do the exact opposite of the "squash pen spring" trick. You need to stretch it out quite a bit, then snip off all but about a quarter-centimeter from the trigger bulge to the top of the spring, like before. Doing any or all of this will result in great trigger feel, better speed, or a lighter trigger.
Thanks for letting me add all of this in, tony. I still think this should be a sticky.