you don't want to get it as tight as possible. you just want to get it so that there's a bit of up-and-down movement. i put my thumb on the seatstay and wrap my fingers around the tire and tug back while i tighten the drive side nut on my hub. then i push the rim so that it's centered while i tighten the nondrive side, and that makes sure i don't get it too tight. i had a mechanic who had the bike in a stand and tugged the wheel backwards hard because he thought the chain should be really tight. bad idea. sounded terrible and i could feel the grind in every rotation. i was much happier when i loosened it up.