I usually mark the bearing caps so to put them back like they were, then using a dial indicator if you have one, check the backlash (the movement of the ring gear in relation to the pinion) by indicating on one tooth on the ring gear, set at zero and move the ring gear back and forth (without moving the pinion) and write that reading down..
Put it back together as closely as you can to where it's at now and it should be pretty close.