The Dink Network

For the fourth stage, you should definitely be water, since it's easy to see how to slip between the fires, but harder to see how to slip between the little rain thingies. For 2 and 6, you should stay near the bottom of the screen. As RW said, on stage 2, you have to run left and right a lot and on stage 6 you should stay near the middle. It's not easy, it took me 5 tries or so before I finally beat it.

EDIT: Remember this trick: if you ever need mana, just press enter (which pauses the game) and wait for your bar to refill.