Some degree of experimentation is required when determining the correct weight poundage. Your repetition goal is the starting point. Let's say the goal is 10 reps of dumbbell curls. You begin with a weight you know is too light, just to see how it feels (this does not count as a set). Perform a few reps and determine how light it is. If it seems easy, increase the weight by 5 to 10-pound increments until you find a weight that feels challenging, but not impossible. The weight should be heavy enough to perform 10 reps, but 11 would be overly challenging.

Once you become stronger and can perform more than 10 reps with perfect form, increase your weight by 5 percent. The key is the first set. You might not get 10 reps on the second set, but that's OK. As long as a set doesn't fall below 8 reps, you're making progress!