I don't know a lot about muscle structure, etc... it's something I need to be much more knowlegeable about.
One particular muscle or set of muscles that I know I have a weakness in are those involved with throwing a boxing hook (shoulder height).
When I throw a left hook at a punching bag..I feel like I am using the muscles from my shoulder to my bicep. Though I am not sure if other muscles in that are are involved.
I've started holding 3lb dumbbells to assist when throwing that move to start strengthening those muscles because the left hook just always feels "weak" and I have less power then my right.
I figured lateral and front arm raises (with 10-15lb dumbbells) would also assist, but any other recommendations are appreciated.