Beat the eggs and fats first and then add them to the dry mix. The crumb will be much finer than if you followed the recipe directions.

Turn yellow into orange by using orange juice instead of water, add a tsp or two of extract for more orange flavor and put some orange zest in. Use a bit of Triplesec or Grand Marnier instead of some of the juice/water

Devil's food or chocolate cake mix is vastly improved by substituting brewed coffee for the water, ounce per ounce. Make sure it is not too hot.

Add 1/4 teaspoon of salt and a little (1 to 2 teaspoons) of fresh lemon juice to any of the yellow or white cake mixes. In our household, we feel the majority of commercial cake mixes are very sweet, especially if they are frosted, and by doing this, the salty/tartness helps balance the flavors.