Boil the noodles, but not completely cooked, leave them just a little tough. Strain, then put back in the pot with a tablespoon of butter, and lots of cheese. I like to use New York white cheddar, gorgonzola, feta, and a little parmesan, and you pretty much just melt it on the noodles, while you fold everything in on top of itself instead of stirring. You can tell when it's done because the noodles aren't tough anymore, and you should have most (but not all) of the cheese melted. There should still be a few lumps here and there, but the cheese should be stringy (like the cheese on a pizza when you take a piece from the whole).
Doesn't really sound appetizing, but it's the best mac and cheese I've had in my life.