Solution #1 (Step 3)

Step 3 -- Form cross on last layer

The first two layers should now be completely correct. From now on, turn the cube upside-down, so that the first face (white, in my example) is the D face. It will remain this way until the cube is complete. The reason for this is just to make the manipulations a bit easier to perform.
On my cube, green is opposite to white, so I will refer to the green face as being the new U face for our purposes. We must now try to form a green cross, out of the green center, and the four edge pieces that surround it.

There are 4 possibilities:

• All four pieces are correct, and you have green cross on the U face. Do nothing.
• Two adjacent edge pieces are correct. For example, the UF and UR piece have green on the top, forming a sort of L shape, with the center. The UL and UB pieces do not have green on the top. In this situation, hold the cube so that the UF and UR pieces have green on the top (as in the example earlier in this paragraph), and apply B U L U' L' B'.
• Two opposite edge pieces are correct, and the other two aren't. Let's say UR and UL are correct (this should make a green line down the middle of the U face). Apply B L U L' U' B'.
• No edge pieces have green on the top. Hold the cube any way (still keeping the green center on the top) and apply B L U L' U' B' F U R U' R' F' (for those of you who want to memorize the moves, you should realize that this is the same as doing the move in the third part of this section, then rotating the cube 180 degrees, and then applying the move in the second part of this section).
  

You should now have the bottom two layers all correct, as before, and a green cross (or whatever the color on your cube whose center is opposite to white is) on the top face.

IMPORTANT: If the bottom two faces are perfectly correct, and you have 1 or 3 edge pieces that show green on the top, then your cube is messed up. Somebody (maybe you!) took it apart (or changed the stickers around) at some point in time. Might as well take it all apart right now, reassemble it correctly and start again.