Here is a chart that I took from Wikipedia, about the color codes to an Ethernet crossover cable. Some other tips are: After you have unwrapped and set the wires up in your hand, that you cut the top as close to 1/2" as possible. Also kind of "let" the wires untwist themselves, naturally allowing them to fall into place.

I haven't made a crossover cable in quite a while so this is a way for myself to remember the exact color codes.