This post goes hand in hand with Cake Dos & Don'ts. I hope these 2 posts help shorten cake newbies' learning curve.
a) Why doesn't your cake rise? »
Short answer: Because you don't follow the recipe.
Long answer:
Egg whites are overwhisked and inextensible.
Whisked egg whites, kept waiting too long, deteriorate and become inextensible.
Eggs/yolks are underwhisked. Don't have enough air