what procedures and precautions should be followed to attempt to start a small pickup truck which has not been used for approximately five years;( it was running satisfactorily when it was parked )?
Well before you do anything you’ll have to drain the fuel tank and the fuel lines-gas starts to go bad after about 6 months.
A fresh oil change and filter for starters. It’s also a good idea to remove the spark plugs, squeeze a bit of oil into each of the cylinders, and turn the engine by hand a couple times to lubricate the cylinder walls and minimize scuffing when you try to crank it, and to be sure nothing has seized up internally.
As said, fresh gas and clean fuel lines are also something to be done, as well as installing a new battery. If all is done without an issue, fire it up. It might take a bit of time for it to catch, and it might smoke and run rough at first, but if it runs at this point you should be good to go.
don’t forget to have a good look at your belts and hoses before trying to crank it up also. Don’t want the belt flying off or a radiator hose spraying coolant everywhere.
may also want to invest in a bit of starting fluid. after 5 years you will definitely need it.
The real fun begins when you get it to start, because then you have the joy of watching all the critters that have made this truck home over the past 5 years go fleeing every which way-some over you haha. It’s a fun way to find out if you’ve got a yellow jacket nest under the car 
You probably won’t need the advice, but push it to a reasonable distance away from any building and highly flammable material and have a fire extinguisher ready.
Is it fuel injected or does it have a carb.? If it has a carb, a rebuild might be in order as the gaskets and seals are probably shot. It could leak and cause an engine bay fire. Lots of excitement when this happens.
Change the oil. Drain and refill the coolant. I’d pull the coil wire or disable the ignition system by pulling the fuse and crank the engine for perhaps 15-30 seconds to get some oil flowing, reconnect everything and go. If the tank was full when you parked it, I’d consider just going for it and starting it. If it was at perhaps 1/2 tank, I’d drain and refill. If it only has a little gas in it, I’d fill the tank first to dilute the old stuff and provide ample ‘good’ gas. Good luck.