I have been playing guitar for a little more than a year, but am having some trouble tremola picking and doing pinch/artificial harmonics.

Tremola picking isn't hard to understand, but is there some trick to it, or do you just have to work the lower arm muscles up a bit to reach those higher speeds?

I completely understand normal harmonics. After that I get a bit confused. Artificial harmonics are using any technique to get a harmonic that isn't normally attainable without fretting, with pinch harmonics just being one of those techniques? Any tips/ explanations would be great.. I can get a harmonic when i hold my pick between my middle finger and thumb and tap the harmonic spot with my index finger, but it's kind of slow.

Also, in a guitar tab, when it says you should A.H, what fre t would they generaly mean? I am asuming you make a 1/4 or 1/2 harmonic to get the same note in a higher octave, but I'd like it clarified.

Thanks a lot!
Pinch harmonics are relatively easy to do, i've been playing for about 4 months and can hit them well, all you do is lightly touch the string with your thumb after playing it, there are certain parts on the string you can hit them for different notes, also, bending them makes them sound good for that high pitched wailing you get in solos =] hope this helps
for tremelo picking, you just hold the pick at a sideways angle and do it, and they all explained pinches. and artificial harmonics is just the "proper" name for a pinch harmonic. i find it easier to do all this if you use dunlop jazz 3 picks, opposed to others, but strumming chords is somewhat harder.
I'm using 1,5 picks, so I think I'm okay there. But when they ask for a pinch harmonic, what "sweet spot" do they normally mean?

Wooh, I think I did a pinch at the 1/4 by the bridge. XD Thanks :-P