Use extra-large eggs.

Always start with room temperature ingredients when baking cakes.

Always whip egg whites.

Pour boiling water on your cocoa powder.

Always sift dry ingredients.

Never melt chocolate in a glass bowl (glass retains heat so use plastic bowl).

The difference between beating and mixing is key (beat butter, sugar, and eggs first, then add dry ingredients, switching to mixing rather than beating).

Freeze dough before baking, not after.