Make sure you disconnect all the wiring, ground straps, fenders, etc.
When I lifted my cab off, I used an engine hoist. I bought a couple of 2x8s and stuck them through the cab on top of the engine hoist arm. I would have at least one other guy help you to make sure things are balanced and so you can guide the cab out easier. However, it can be done with just one person. I do have some pics of the cab off the frame, but none when we had the hoist and support boards through the cab. -->
http://www.shelbournes.net/trucksite/cab_swap4.htm
Or, another way of doing it is getting 3 moderately strong freinds and each of you grab a corner and lift. However, I'd take the seat out to reduce some of the weight. We lifted my cab off the trailer onto my dolly with just four of us and it was pretty easy. It was fully loaded down with the seat and everything. However, when you're lifting it off of the truck, you have more obstacles so that's why I was saying you may need to reduce the weight a little.