There are a ton of factors that go into getting good regens.
Always upgrade facilities when possible, and I mean all facilities. Upgrading your facilities will make you more attractive to youngsters, as well as boost your club reputation which will bring in better youngsters.
As I've said reputation plays a roll, so obviously winning improves this. Also city size, national team success, and your nations love for football effects quality of regens. Don't forget about coaches, there was a myth that dealing with youngsters stat for coaches was important in getting good regens, the consensus now is that this may be untrue. However a coaches high reputation can attract good youngsters who want to play for that reputable coach.
I think I've touched on all the bases here, others may feel free to add or correct.