FIRST RULE FOR TRUCK LIVING:KNOW HOW TO WORK ON YOUR VEHICLE!I know it sounds obvious,but get a good shp manual for the year and model(chilton's are the best in general use),and understand how to turn a wrench.Classic example happened to me in the Snake River region of Idaho back in 2001.The rear end blew out on my old truck on the interstate,got it towed to a old country garage.Bought the rear out of a similar truck from a local boneyard($200),and by helping the mechanic;got the whole thing repalced including new U-bolts,seals,etc. for another $200.Have had to change voltage regulators on the side of the road($15 worth fo parts if you do it yourself,$75 for a garage),starters(as low as $19,$125 for a garage),alternators,belts,etc;even a compleat clutch.It doesn't matter if you have never worked on vehicles before,$100 worth of Sears wrenches and a manual will save you a world of heartache.
Pack light:I know it seems like you can stuff everything you ever wanted into the truck,but think in terms of what you NEED,verses what you WANT.
If you don't want the cops to find it,DON'T PACK IT!Transient trucks seem to be a cop's delight,and it would be a shame to have it impounded after a dog going thru caught a "whiff".
When "dry camping",don't stay more than one night in the same lot.
Two spare access/ignition keys,both attached to some place that they are safe under the truck.I cover mine with Cosmoline and bolt them to a area where it would take the equivilant of a cavity search of the truck to find them.
Put together a "chuck box"(I use an old wine crate wth a lid that can double as a low table)with a couple of mess kits,frying pan,billy can,and a weeks worth of easy to eat,easy to prepare food.Cycle thru the food ever couple of months,replacing what you eat.Nothing worse than being stuck in the middle of nowhere and hungry while waiting for a change in situation.
Toilet paper.Need I say more?
Water.I keep a 5 gal. plastic jug with a handpump in a rack when traveling.Good for drinking,tea,spongebaths(learn to love Doc Bronner's Peppermint Soap),and the ocassional radiator boiloff.
Keep a single $100 bill and a roll of quarters for each person.DON'T touch it,smell it,fondle,etc.This is your "buryin'money",an old cowboy thing.If everything goes to hell compleatly,you got a stake to a new start.Keep it on you person at all times.
OBEY THE TRAFIC LAWS,AND DON'T DRINK AND DRIVE!