How do I alter a cake mix to make it more dense. I've seen several ideas on the net (add more eggs, less egg, shortening in place of oil, butter in place of oil...) I'm utterly confused, please help!

Check out the WASC (white almond sour cream) cake recipe in the recipes section - it is a great dense cake that is very moist as well, and tastes awesome. Plus you can change up the flavor of cake mix to make different cake flavors.