My preferred grilled cheese:

wheat bread
shredded sharp cheddar cheese
tomato slices
spicy brown mustard
olive oil

Spread olive oil on one side of each piece of bread, mustard on the other side. Stack up a buncha cheese on the mustard side of one bread piece and throw that on your grilling apparatus of choice. Grill it open-faced until the bread is browned to your satisfaction, throw a couple tomato slices on there and the other piece of bread on, olive oil side out. Flip it and brown the other side. Or just throw the whole thing in a george foreman grill or sandwich maker and take care of it in one step.