Have you ever read the Evil Overlord List? That, and some of the antics of certain villians inspired me to write these. Please, add some of your own!
1. The entrance to my fortress will be kept shut and locked at all times, unless it's in use. Also, the levers to open the entrance will be on the inside, where no adventurers can reach them.
2. I may be a god, but my priestesses are only mortal. Therefore, I shall instruct them to wear heavy armor, even if they don't look as sexy or stylish as they do in robes.
3. Even if I can cast spells silently, I will not explain my evil plot in the middle of a battle.
4. No matter how powerful I am, I must destroy my enemies whenever I have the chance. Leaving them alive will only lead to trouble later.