Step 1: Supplies.
Okay, you'll need:
A hat, I used a cheap felt top hat from UsToy.
El wire kit. I bought mine from Thats Cool Wire. Link to the kit I bought: http://www.thatscoolwire.com/store/item.asp?Category=168&SubCategoryID=124&GroupID=&SKU=WY-NH-LZ-3V
You'll need enough for the rim of the hat your working on. (Or whatever design your doing)
To attach the battery pack to the inside of the hat, I used a piece of stick on velcro. (The hook side)
A needle, and fishing line. (I used two really long pieces, I ran out the first time.)