I haven't gotten to play the Pit MU much (I did play ALSM once or twice with Luigi) , but I can tell you to make sure you don't give him free damage by eating Uairs if he is on the ledge.
If you don't want to just run off and try to Bair (be careful about this, since you're put in a bad position if you fail), just shield arrows if he ledgedrops -> jump -> arrow, because if you go too close, he'll uair your feet.
Check the vid thread and see if we've got some Pit matches. Pit can be really campy if he wants....just try to keep relatively close to him, or you'll eat arrows all day. When you get inside, our jab should > his. Even if it's just a jab combo, try to get damage in when you get inside.
Also, do not challenge his Uair if you are above him
Edit: YoshQ has a 2 matches vs. Pit in the video thread. I'd go watch them.