[MrPoptart]

Find a song or a few songs you like around lv 25 and keep playing it until you have no misses boos or averages. Then do that again with another slightly harder song. Before you know it, you'll be tackling lv 40 songs.

You can try messing around with your speed if it seems like arrows are too close together. it might take a little while to get used to though. If you wanna practice a song at a slower speed you can change your "rate" to .5, for example, for half speed. Your score won't save unless your rate's at 1 though.

Edit: this was a great thread recently about improving and what a lot of the options mean. Some of it might be a bit too advanced atm however.