First thing you'll need to do is trim off about half an inch of the insulator. Alot of you will want 3/4" to an inch to work with at first. In the end you don't want any more uninsulated wire than you have to.
DO NOT take off anymore insulation than you need
DO NOT nick the wires. If you cut the wires even a little bit cut it all off and start over again.
After you've removed the insulator inspect it to make sure you didn't cut into it anywhere. If you did go back to the previous step. If things look OK then you can start straightening the cables and putting them in the order you need them. I suggest using something like the edge of a table to help you straighten them out.
When you're done they should be in the right order and and sitting fairly closely together. After that you'll be ready to trim. Make sure that you get them as straight as possible! If any cables are longer than the others your cable will not work properly!
After you believe you have the cables straight go ahead and insert them into the RJ45 end. After you push them in as far as they'll go examine it closely to make sure they're in the right order and they're all the same length. In the picture below I put pin 1 where pin 8 goes in 568A wiring. That's just to make sure you guys are READING :)
If it all looks good then go ahead and crimp it! Make sure you put plenty of muscle into it. You want to make sure you make a solid connection with all of the wires.
Now when you plug your cable into your computer and switch the light should come on if it's working properly. There's also cable testers you can buy but I don't want to get into that today.
Now you know how to make your own cables. Expect some basic networking guides in the near future.