The Smurfs has a built-in tutorial, so there's not really much left to the imagination. Play through the first 7 levels and the next 12 should be a breeze. Because the game is linear, make sure you collect as many candies, cakes, and crescent moons as possible for extra lives and a date with Smurfette. Remember to keep switching over to the Baby Smurf screen to see how he's doing. Otherwise, it's all standard platform fare.
Level Select
Select "New Game" and then "It's no picnic" difficulty. Press X and on the next screen, after the video, enter L1, Up, Up, Down, Up, Left, Left, Up, R2.