First of all, take your time and enjoy the project. If something isn't working, walk away for a day or two so that you don't do something you'll regret. This is supposed to be fun.
Label and sort parts as you remove them. Categorize them as 1) usable as is, 2) usable with some work, 3) swap meet stuff, 4) scrap metal or recyclable, and 5) trash. Don't get rid of anything that you take off the truck until the project is finished, because you may not be able to find or afford a replacement.
Don't be afraid to take photos and notes during disassembly. You wil find they come in handy during reassembly.
Plan out the entire truck as much as possible before doing anything. Having a clear idea of what you want the vehicle to be before you start buying parts and building will save you time and trouble later.
Hope this helps,
Dennis W. Parks
author of automotive how-to books