3. The Look
If you look good, you feel good. The way you look can make a big impression on others, so make sure you dress the part. There's more to a villain's appearance than some wizard's robes, a suit of plate mail or a wealth of cybernetic limbs. Embellish it! Make sure you look dangerous.
The first thing to think of is a colour scheme. Now, I know what you're thinking and it's 'black, black, black' -- and yes, black is a great colour for a villain to wear, but the thing is the heroes have all started wearing black too because they think it's cool. Only wear black if you're certain that you can look cooler than the heroes. Reinforce your robes with leather. Embellish them with silver embroidered skulls. High collars are in. Skull caps are in. Black gloves never go out of season. Make sure your materials are of the finest quality -- silk, velvet, leather, or, better still, the hides of exotic creatures. If you're evil, chances are you're not going to be too concerned about animal rights. Go wild! Treating yourself once in a while can't do any harm.
Consider other colours, though. White can look very sinister. Red's the ideal colour for any fire user -- try combining with gold and black so you look as fiery as your spells! Midnight blue is the new black. Green is the basis of good camouflage; try combining an olive drab with black for a severe, military look. Go for a consistent look, and be careful if you combine colours. I'll say right now that blue and green should never be seen. Aim for a consistent look with one colour predominant. If you're still stuck for a name, the colour of your clothes is a good place to start. Look at Saruman the White (later Saruman of Many Colours), Gandalf the Grey (later Gandalf the White), Rackhir the Red Archer, or even Robin Hood, who was famous for wearing Lincoln green. It's just as important as the gimmick, if truth be told.