Ok, I'm gonna assume that you've already read through this part of the FAQ.
(144856.30)Now read it once more, all the way through.
Now, to put it short and sweet, once per week, on Friday, the training update takes place. At that point, the training looks at what you set in the "Training" page, for example, "Pressure" for "PG/SG". Then it looks for what players played minutes at PG and/or SG from that week's games (in this case, the Sat. League game, the Tuesday lg game, and the Thursday cup/scrimmage game), totals them up, and applies the increase in the skills that "Pressure" trains (which is mostly outside defense, some inside defense, handling, and driving). The players with applicable minutes for the chosen training type are listed in the "training" box of the "manage my team" screen.
To get the full benefit of the weekly training, players need to get at least 48 minutes. Above 48 minutes doesn't help, but below 48 rapidly reduces the training benefit.
That's basically how it works. and here are some practical tips.
Get a level 4 (advanced) trainer. The trainer level influences how much the player improves during the update.
Decide whether you want to focus on training guards or training big men. It's usually not practical to switch between each, so train one type, and get some cheap veterans for the others.
Find some trainees, preferably 18 year olds, cheap off the transfer list, and get ones with "star" potential or above. Figure starting salaries of $3500, but also try and avoid anyone with atrocious or pitiful in a skill they'll be trained in.