Re:bringing up lagging parts ?
unilateral movements... e.g. DB exercises
Start off with your weaker arm, and only do as much as your weak arm.... Gradually over time it should even out, As I'm sure this has been a problem with a few people (Me including at the beginning of my training)..
Another option - i did see someone in the gym curling with different size dumbells as he was 'trying 2 make my other arm stronger m8' - Although I probably wouldnt advise this!!
Eat big - Lift big - Grow