Packing...ha! I'm borderline OCD when it comes to packing. I'm actually packing as we speak for our DV trip tomorrow with 8gals of extra fuel and 8gal of water etc.
My packing usually starts a few days in advance because I arrange and rearrange stuff, try different boxes, containers etc to find the best location for things. Having a roof rack helps a lot but I do my best (if possible) to keep the weight up top to a minimum. Here are some things I've learned from others and from experience:
1. Don't bring the whole living-room and the kitchen sink, keep the weight as light as possible and in the camping spirit. This doesn't mean you have sleep under a tarp either. Just like with finances budget things i.e. allocate one box for food, one bag for clothes etc as appropriate for your truck and family.
2. Use the roof (cargo box, roof-rack etc) for camping equipment (tent, pads, chairs, table etc) that tends to be bulky but not too heavy.
3. Build a storage platform or drawers efficiently to allow storage below and on top of it without wasting the precious cargo space.
4. Use containers and strap them down well so they don't become projectiles in case of an accident either on-road or off.
5. Keep the heavier items as low as possible and in front of the rear axle (preferably in the middle of the truck if possible) or at least right over the rear axle.
6. Light, bulky items can go towards the very back of the truck i.e. behind the rear axle.
7. Check everything again to make sure it's all strapped down.
8. Weigh your items and accessories to know where you stand in terms of GVWR.
Roof-top canvas bag.
Low-profile storage platform ($30)
Day trip setup (2 adults, one kid and 50lbs dog):
Four day setup with solar-shower, porta-potty etc (2 adults, one kid):