A *typical weight set is 3 sets of 8-12 reps per movement.
The end of the third set should be difficult. If it's not, move up a weight, or do 2 with the 10#, one with the 12#.
Again, the above is standard/typical. Varying the weights per set is good, for variation, and to work your muscles to exhaustion.
I've always read that to help with endurance, do the 3 sets of 8-12, but to build bulk fast or work with fast twitch muscles, vary the weight.