Farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm, farm.
That, and one thing I don't like about most nasus players / top players in general is that they basically just play a separate game. One you do sufficient damage, I would suggest start to try to split push other lanes or try to do something in a team fights. Don't just stay in your lane for 30 mins and wait for your team to win for you. 80% of the games I play with nasus top do this and it drives me absolutely insane