Misconceptions
Many people try to solve a Rubik's cube one side at a time. However, the nature of the pieces, and the fact that there are three stickers to a single cube, mean that the best way to solve a Rubik's cube is by layer.
Orientation
Choose a side to represent the "top" side. This is done by analyzing the center squares of each side that does not move. That means that the center square of the white side is always opposite the center square of the yellow side no matter how much you turn the other pieces.
Layers
Start with the top layer of the Rubik's cube and then work downward. As you move the pieces, pay attention to each side of the individual cubes. There are two stickers on all the edge pieces and three stickers on each corner piece. It's important that each sticker is in the correct position.