Many folks, and even some coaches, don’t put much thought into the accessory movements in their training programs. They pick a few standard “cookie cutter” exercises and do a few sets after the main movement and call it good.
This is a phenomenal way to stagnate progress and potentially cause injuries.
Any exercise that is chosen for a program must have a purpose. Yes, that means ya’ll beginners that weigh 145 lbs. soaking wet really don’t need to be doing 6 sets of wrist curls.
The goal is to target your weaknesses with accessory lifts; be the weakness visual or physiological.
For example, if you are unhappy with your chest development, should your accessory exercises be focused on bringing up the triceps (close grip press, JM press, tricep extension, etc.)?
No, the main focus should be on the chest with movements such as flies, DB press, pec deck, etc. This does not mean you should have no exercises dedicated to the triceps, you must maintain balance; they should just not take precedent.
In the same manner, but from a physiological standpoint, if you are missing the lockout on the bench press but are strong out of the hole, you should work on strengthening the lockout muscles (triceps) and let your chest take a back seat in the accessory movements.
These weaknesses can and will change over time and your exercise selection should change concurrently. This is where it helps to have a coach as it is not easy or fun to work on what you suck at.
Trust me, I know. It’s a lot more fun to go in the gym, do the lift you’re best at, and leave feeling like King Kong but all this does is massage your ego and that’s not what needs to be trained.
TLDR; train the things you suck at during your accessory lifts. Your physique and 1RM will thank you.