Plant Sun-shrooms to produce sun. While you continue collecting sun, plant Puff-shrooms to kill the first few zombies. Then, plant one column of Fume-shrooms and a column of Wall-nuts to defend yourself against the Screen Door Zombies.
You might not be able to grow all of your Sun-shrooms before the final wave. Try to waste as little time as possible in planting them.
If you still have time before the final wave comes, plant Peashooters and Repeaters for more offense.