How do you keep Velveeta cheese creamy?

How can I make my cheese sauce creamier?

I know it seems that Mac 'n Cheese should be an easy thing for a beginner. Is not it. Without a solid recipe, even seasoned chefs can royally screw up mac'n cheese. Generally, it starts with a bechamel, also known as a white sauce. You're right, that starts with a roux that requires flour or at least some kind of starch. Once you have a good white sauce, add the grated cheese. You're right again, pre-shredded cheese is not a good idea. Pre-shredded cheese is covered with cellulose so that it does not clump in the bag. That doesn't make for a smooth melt.

Alton Brown's stove recipe is about as easy as homemade Mac'n Cheese. I would recommend mastering this and then move on to recipes (written and highly rated) that begin with a bechamel. And grate your own cheese. AB's Herd Mac 'n Cheese.

EDIT: One more thing - Mac 'n Cheese Cheese Sauce is an application for which higher quality (read that "expensive") cheese may not be the best choice. Good quality, expensive cheeses tend to be aged and melting with what you might think was grainy in texture. Some people go so far as to use American cheese (gasp for air) or even velveeta (gasp for air) to melt it smoothly. Not sure if I would recommend going this far, except for youthful taste buds. For me, a happy medium (so to speak) is the private label medium cheddar. AB's recipe calls for spicy cheddar, but it has other ingredients that add to the potential graininess.