Id say use the weights you can make all the twarget reps with. Everyone is different so the weight you will use will differ to what I would use.. Start your first set with something light and if it was too easy .. add more weight for the next set .. and do it that way.
Perrin
-------------- "There is no age limit on transforming your life. No rule that says that after a certain age you are simply the way you are and that's it. Change not only is possible at any time but is essential." Rick Pitino