We make ours like this (or variations, depending on what we have on hand.)

Lettuce
Kidney Beans (rinsed and drained)
Grated cheddar (or any cheese you prefer)
Fritos
Catalina Dressing


Etras or variations can include

jalapenos
hamburger meat seasoned with taco spices
garbanzo beans
ranch style beans
tomatoes
salsa

Easy and a favorite in my house!