Do as noted above, and go full rounds of turning each spoke the same as the others. When you reach the point of the spokes being reasonably tight if the rim is still way out of whack then you can safely assume that the wheel itself is physically bent.
I apologize for being blunt, but if you have to ask a question like this I would not recommend you work on your friends' bikes, and you need to learn that wheel truing takes more than a tension meter. You have to get the wheel in good shape, close to final tension first, then use the meter. Otherwise you are trying to tension one spoke in relationship to others that are way under tension.
The "trick" is understanding the purpose of a process and the interrelationship of parts in a system (like a wheel) not just the procedure.
Last edited by cny-bikeman; 09-13-10 at 08:02 AM.