When you're going to drop in on a quarter pipe what you want to do is you want to roll parallel to the coping. Get as close as possible. In the beginning, if you're really weary about dropping in or you've had a bad experience, you can actually drop into a Smith and let the front peg hit the coping and then fall in. On something a little more mellow you really can't drop into a Smith, so you just have to kind of drop in head first, no pun intended. You want to go parallel, kind of lean to the side that the transition is on, and just pull back slightly and match your wheels to the transition.
As you're coming in, you're going to Hawk and you want your front wheel and your back wheel to match the transition so that as you come in you're not hanging up, you're not looping out, you're not going forward... you want everything to kind of match and be mellow so that as you approach the quarter pipe you're not going to have any issues. You don't want to go sideways, you want to go straight down the transition unless you're going really fast, in which case you can do a little more of a carve. That's as easy as drops can get and that's how you'd do a drop in.