I have started paying attention to every exercise I do. I try to slightly change grip positions etc to see how my body reacts and also to find which muscles I am hitting, as well as the areas. This is a simple way I figured out which area of the muscle I was hitting when curling. Granted what I say may not be true to some, but for me, I can feel and understand what I am working.
Depending on the stress caused on joints etc. Some of the ideas may not pay off over the long run.
*Back hand face down (Palm facing up)