You've gotten a lot of good advice so far so no need to repeat everything. Being someone who plays both games (though admittedly, I'm relatively new at each), the two differences that stand out to me are:
1. Managing your players playing time is a HUGE thing here, and thus setting lineups (not only starters but your backups) is much more important than in HT. Basically in HT, make sure your trainees play 1 out of 2 games a week at their position, and you're done. Here, you basically MUST get your trainees 48+ minutes, and so you're trying to juggle player minutes at sometimes multiple training positions, over 3 games a week. Not to mention you have to monitor minutes for ALL of your players, not just trainees, because minutes played translates into game shape (equivalent to "form" in HT), and playing either too few OR too many minutes per week will send your players' game shape into the tank.
2. It is far more crucial to develop & train multiple skills here than in HT. Partially because of performance (your center with Outstanding inside scoring but atrocious inside defense is going to be a liability, not a help), partially out of salary management (the full math is complex but a player with one really high skill and all the rest low will have to be paid a stratospheric salary--despite the fact that their overall performance will be far weaker than a player who has developed 3, 4, or 5 skills more or less evenly good without being spectacular at any one of them), and partially because if you don't train multiple skills you will actually gimp your training, as the training engine is designed to slow down training speed in a given skill if that skill begins to outpace its other, related skills. So if you're training a point guard and his ball handling skill is already 2 or 3 levels higher than his passing, outside defense, etc., and you try to keep training ball handling anyway, it is going to take an increasingly greater number of weeks before you get a "pop."
Oh, one more note that might be helpful, just like the Set Pieces training in HT is independent of your trainer level, and thus a nice skill to train during an off-week or something like that, here in BB there are two skills like that, Stamina and Free Throws. Both are independent of trainer level and independent of even whether a player gets a single minute of game time that week. Thus early on, before you've had time to choose what position(s) you are going to train, hire a trainer, etc, etc, you might want to stick your training to Team Training for one of those two skills until you can get your feet wet. (If a lot of your team seems to have low stamina...I'd say mediocre and lower...than training that might be a good idea. Otherwise, Free Throws is a good choice, as the newbie default players are often horrible at them and it's not uncommon to see after a game that your team, as a team, shooting less than 50% from the free throw line.) Oh, and also, both Stamina & FT's tend to pop ever 2 weeks or so, which means even one week of training them will net you at least a handful of those little green up arrows next to your players' stats...which is always encouraging to see for a new player starting out.
