If you do the first level in the second world you get lots of lives.First you go through one of the warp pots (green and blue stuff sticking out of the ground)and then grab the feather and then hit this oversize coin and it should say 600 at the side of your screen.That is how many coins are in the area.Do this alot and you will get alot of lives in no time.
Go to single player and go to super mario world and go to yoshi's island and git yoshi if you beat it go back and if you didn't beat it finish the level then go back to yoshi's island and go to the place where you got yoshi and keep doing that over and over
If you have top secret area, go get a yoshi there. Then leave and re-enter. Hit the block there that contains a yoshi to get a one up. You can do this as many times as you want to save up for a hard level.
On the last stage of Special World which is called Funky get to the end of the level. There are words written out in coins which say YOU ARE A SUPER PLAYER ! It really shows how great you've become at this game, because getting to and getting through this level isn't easy. Congratulations.