This is the base guideline that I always use:
8 oz. angel hair pasta (1/2 box)
2 cups diced, cooked chicken*
2 (10 oz.) cans cream of chicken soup, undiluted
1 cup salsa
1 cup (8 oz.) sour cream
2 cups Mexican cheese blend, divided use
dried parsley, for topping (optional)
Sometimes I mix up the cheese and use Italian cheeses and throw in black olives, fresh spinach, or thick sliced tomatoes, and sometimes I use the shredded Velveeta with a "top crust" of parmesean with broccoli thrown in.
Edited to add: the sour cream is just for creaminess and can be left out. Also, can substitute one or both cans of chicken with mushroom soup (it's good that way too).