Pack and load
Assemble your stuff, check it against your list, add things you think of, and remove marginal items you probably won't need. This step is especially important for backpackers, who need to hone their pile down to the bare essentials.
Consider your vehicle. Is it full of gas? Has it been recently serviced? Is it backroad-capable (if it needs to be)? Does it have a spare tire, jack, lug wrench, jumper cables, and coolant? A dependable car is a must. If you have a cell phone, bring it.
Assemble your boxes, bags, and other containers. Group things that logically belong together: for instance, put clothes with toiletries in their own bag or compartment. Try to keep what you'll need first, often, or urgently as accessible as possible. All this will help you spend less time searching around.
Be sure you can physically carry all the gear. This is very important for backpackers, but also a consideration for car campers. As you pack, cross things off your list. Load them into the car, securing fragile or spillable things by placing heavier, bulkier items on the bottom.
Fresh air, gorgeous scenery, sunshine, and starlight: A great camping trip packs many pleasures. Packing right will help you enjoy them all more.