I woulden't even pan until you have all of your levels set. Panning is the last thing I do when mixing.
There isn't a "set" spot for things to go, but there are many popular areas for drums-
Snare-usually down the middle, I tend to slightly offset it left or right a tad to keep the main vocal track (If i have them going down center, especially with a female vocalist) from fighting with it.
Kick-Middle
Toms-at about 10 o'clock for the highest, and go from there with the rest.
Hats-slightly to the right or left, just past the snare
Overheads-I really don't like to go totally hard left and right with them, I would rather fill that area up with some effect returns, but they are pretty far out there.
Don't solo tracks when panning. Slowly adjust the panner until you hear the instrument "pop" into place. It also helps to check the mix in mono to see if anything disappears. If it does, you can fix a lot of that by adjusting your panning.