50NL = Less limping, more positionally aware villains, more preflop aggression (3 betting etc) less passive post flop play, higher regs to fish ratio, nitty or cock waving idiot regs that is for the most part.

Basically it's just tougher. There isn't a magic secret to beating 50Nl having beaten 10NL, it's just a case of improving your game by posting hands, reviewing your play and yeah thinking about more stuff.