To some extent, it depends on the tactics you are using and the team you are playing with.
Playing one of the big 4 in the
Prem, keep it simple and try not to tweak out training schedules. Players already have great stats and you want them maintained.
With lower league teams you might want to tweak them a little more.
Another thing to keep in mind is that you need the coaches to be able to get the real effects out of training. So, go out and hirer as many solid coaches as you can to get as many stars as you can for each training category.
Trainng schedules are important, but without coaches capable of carrying them out...forget it.
As for training shedules, they are all over this forum. Looking in Cleon's tactics bible for links. Seasoned Alcholic has the most comprehensive set you could imagine!
But for starters, try to keep it simple. I use a 442 and I create Keeper, D C, Fullback, M C, Winger, Striker, TM schedules. You could even forego the keeper sched as the default one is not so bad.
Hope that was helpful.
Good luck!