To achieve the perfect moistness in your Cinnamon Swirl Cake, there are several key techniques to follow. First, ensure your butter is softened correctly and at room temperature; this allows it to cream with the sugar more efficiently, trapping air which contributes to the cake's fluffy texture. Additionally, using room temperature eggs and milk is crucial, as it helps create a uniform batter that will rise evenly. When it comes to mixing, be careful not to over-mix after adding the flour—stir just until combined to avoid developing too much gluten which can lead to a denser cake. Lastly, keeping a close eye on baking time can prevent over-baking, which is a common cause of dryness. The cake is done when a toothpick inserted in the center comes out clean or with just a few moist crumbs attached.