How do I get my players to improve from year to year.  Is there anything I can to maximize their growth and improvement.  What works the best.  Is it coaches?  I would like my younger guys to achieve their projected number.

Wouldn't everybody?

Playing time, coaches, and one season at each level. Don't repeat seasons at the same level. Prospects with low patience should move up a little faster.

Some owners will start their best prospects in LoA instead of Rookie.

There is lots of variability Most of the time development falls short of projections, and injuries often cause setbacks that are not fully overcome.

Expect disappointment.

It's just like real life. Every prospect in real life is heralded as "The next someone-or-other" but they rarely turn out that way. So it makes sense that so few players in the game live up to their actual projections. You should use projections as a general guide rather than a benchmark.

Maximize training to 20m.   That develops their physical skills.  

Hire good coaches and give them plenty of playing time.  That develops their learned skills.

As for levels, a true prospect should be in AAA by the time he has to be protected on the 40.  
4th - AAA
3rd - AA
1st/2nd - RL/LoA/HiA(doesn't really matter how you make that happen).