To achieve perfectly moist and fluffy vanilla yogurt cakes, several factors are essential. First, when creaming the butter and sugar, it's crucial to whip them together until the mixture is light and fluffy, which incorporates air and helps create a lighter texture in the finished cake. Moreover, be cautious not to overmix the batter once the dry ingredients are combined; overmixing can lead to dense cakes due to the development of gluten. Additionally, using fresh ingredients, particularly baking powder, ensures a good rise, creating that desirable fluffiness. Finally, monitoring your cakes closely while they bake is vital; err on the side of underbaking slightly, as the cakes will continue to cook a bit after being removed from the oven. This helps maintain their moisture level.