We got the pig in the ground and the beer on ice, all my rowdy friends are coming over tonight.
Bill, the way it's done around here, (Arkansas) is dig your pit about a foot larger on each side than yer pig is. Dig it about 2 1/2 ta 3 ft. deep unless your cooking a really big hog, Start yer fire in the hole and keep burning until you have about a foot of coals a little more if it's a big one.
have some sand on hand, and put a few inches over the coal right where the hog will lay,
wrap your hog with wet burlap bags, couple of layers, some people around here also wrap chicken wire around the hog at this time (keeps him from falling apart when you lift him up, lift with the wire not the animal)
layer several layers of tin foil over the spot where the hog will be, tie some wire to the chicken wire (several places) tie the lifting wire to some 2 x4 s to lift with set the hog in the ground, slip out your 2 x 4s, add a little more dirt or sand around the hog, not too much
now this is where we do it a little different, we don't cover the whole hog with dirt, lay a sheet of sheet iron (tin) over the hole and put some sand around the edges of the sheet iron to seal it,
all your doing with the dirt on top of the hog or the sheet iron is controlling your coals and making the coals last for a long time.
when you cook it for 12 to 15 hours you don't have to dig it up, just uncover your hole and slip the 2x4s back into your lifting wires and get some hellp and lift him out and onto a table, then just dust him off and take the wire off , uncover and eat.
of course ya season him to taste before putting in the fire, also a lot of people put a stick in his mouth and prop it open, to let all the moisture out of the body cavity. also makes it easier to put an apple in.
hope this helps.