I was recently given a tip by my teacher at school on how to get the most moist cake.
Immediately after you take the cake (or cupcakes) out of the oven, you just pop them into the freezer for a few minutes. My teacher explained that while the outside cools, it will seal the heat and steam on the inside, leaving the cupcake more moist! I have tried this tip, and have to say it really works.
Special thanks to that teacher!