Assuming you are working with a well-balanced formula, when a cake falls, peaks and cracks, or has poor texture, the first thing to consider is the oven temperature. The next is the proportion of ingredients (how they are weighed or measured). Incorrect substitutions without adjustments are often the problem; jumbo eggs instead of large, all purpose flour instead of cake flour without making necessary adjustment, as well as old baking powder can be a problem.
Assuming you are following directions precisely and have accurately weighed or measured the ingredients, the most common cake problems and causes are:
Batter not sufficiently folded with beaten egg whites
Too much leavening