There is a saying -"It is better to act now and ask forgiveness later then do nothing." Or words to that effect.
Now don't go crazy here and start doing insane things and say but "Brett said it was better to ask forgiveness than do nothing" - you are responsible for your own actions! And this is a fitness blog so quit scheming for tonight.
And my point is....
Waiting for the perfect program or perfect exercise to hit "this" body-part or the perfect diet etc... to begin working towards a goal is paralysis by analysis. Your routine and your life do not have to be perfect to begin - they just have to be.
Your program has to have structure but needs to be open to change. You can begin on your own but find you need the advice or program design services of a professional (such as those on my website). But begin or if you want to begin a professional program - don't wait - get in touch with someone and get started. Good intentions and such...the road to not accomplishing your goals is paved with them.
Instead of wondering which assistance exercise will get you squat or bench or _________ moving - how about working on your squat or bench or ________ form. Work the exercise then once you find a weak section of the exercise you will have a better idea of how to pick an assistance exercise. Place your attention on what you want to improve in and keep it there.
Act with confidence and be decisive - learn and research to aide you in this don't act blindly but act.
I made the decisive decision to move across country and establish a new internet business. I did not wait for things to be perfect - I acted. And I'll let you know how it turns out.