Also add a bit of the water you used to cook the pasta, which has some of the starch from the pasta in it, which will further emulsify, or pull together, the sauce. Add whatever seasonings you like plus salt and pepper to taste (I love the combo of Dijon mustard and something spicy, to keep the whole thing from being too one note, and give it all a bit of zing). Then you slowly add the cheese until it is melted and all incorporated-adding the cheese slowly prevents the cheese sauce from becoming grainy or oily.