Having parted a truck earlier this year I prioritized my dismantling in this order:
1. Stuff I probably won't need and is in demand - i.e. will sell quickly (shocks, engine ancillaries, brake calipers, drivetrain components)
2. Stuff I probably will need and should remove so it doesn't corrode, get moldy, get chewed on by critters, etc. (sensors, computers, electrical components, interior parts, belts, hoses)
3. Stuff I probably won't need any time soon and it doesn't matter if it stays on the donor truck (axles, wheels, trans, TC, engine, glass, plastic interior panels)
I would imagine this order might be different depending on where you live and what kind of storage facilities you have available. If I had room in a garage/cousin's warehouse I wouldn't remove anything from the truck until I needed it. If the truck was sitting outside in New Hampshire I'd strip it before winter set in.