There are a lot of frames of thought on this. The truth really is that no one knows. For the longest time owners were under the impression that a players 'makeup' was the most likely factor to determining if they would receive ratings bumps, how often and how big the bumps would be.
Some of us now believe there is some unknown formula we can't see that determines how much a player will progress, how much their ratings bumps will be and...... to a degree how often (I say to a degree because most players will receive around the same number of ratings bump 'opportunities' in a year but the part in the season they happen will be entirely different.
My biggest proof of this was between
Jimmie Merced and
Brent Hammond. (some of this you will have to trust me on as injuries have skewed the players progress from their natural progression) Both were drafted in the same season, both followed the exact same progression through the minors, both received relatively the same amount of play time. Merced was 2 years younger which typically means he would receive more of a ratings boost but Hammond has a higher makeup which can mean a larger ratings boost. For this comparison we will only be using batting as a speedy 2B tends to get more fielding / running boost ratings then a offensive C.
Merced's growth cycle was aprox 6 points, 4 points, 1 point, 1/2 a point
Hammonds growth cycle was aprox 9 points, 7 points, 5 points, 1 point.
Hammond was older but had a higher makeup. Does that mean makeup wins in development over age? Again, I'm not sure. Sometimes I have guys with Makeup of 99 that never come close to their draft progression whereas guys who have makeup of 43 exceed it.
I would say don't worry too much about shrewd management or promotions. For me, I try to get my prospects as much playing time as possible regardless of what level they are at (to the point I have some position players in the minors at 50 health starting games) I promote at the end of the year (no one seems to know if the end of the season bump is true or is just rounding up the minor bumps we can't see. Regardless, I like to see the bump) and try to figure out which works best for you.
The one consistent I can say (I'm sure some of the other guys will dispute me on this) is if you make a trade before the season starts, a player doesn't seem to get the spring training bump. They will have 'trade' on their ratings bump and, from my experience won't get a ratings increase at all. I try to avoid trading for or trading away prospects during spring training if possible.