There are a few things that you can do! First, make sure that you have about the same amount of batter in each pan. I use my kitchen scale and weigh the pans for this step. This will also ensure that your cake layers are about the same thickness after baking. Second, make sure that your oven is thoroughly preheated (for at least 15 minutes) before baking. Lastly, turn your cake pans around (gently so as to not cause the cake to sink!) about halfway through baking.