I dont know if i'm the only one, but i use the middle finger to hold down the D and G string, and use the ring finger (the one between the middle and pinky) to hold down the B string. The leaves the pinky free to do hammer-ons on the 2nd and 3rd fret on the high E string. This is what i'm most comfortable with. If i'm playing very fast, i can get away with just using my index just by putting it flat, which is really cool, as that means you can do pull off with your now free middle/ ring finger and your pinky...
I'm pretty sure this is wrong, so dont try this first, but if the others dont work try it.
(you can prbably tell i learnt chords from tab... i did have anyone or a book to show me at the time, so my friend just sent me some chord tab...)