Summarize:

Are your fingers long, your hands narrow? Do you have perfect cuticles and nicely-shaped nails? Small knuckles? Those are wonderful signs that you have good looking hands. Make sure you have a smooth, even complexion. Don't assume makeup will, well, make up for your imperfections. Birthmarks, freckles, moles, scars, crooked fingers, and irregularly shaped nails will severely limit your progress as a hand model. Pay special attention to your thumb; it'll play a huge role in many hand shots, so it needs to be good-looking. Here are some other things to consider:  Inspect the back of your hand. If you're a woman, it needs to be narrow.  Though women are more often hand models than men, men can be hand models too. Just make sure you don't have hairy knuckles. Don't get discouraged, though. There are a number of different types of hand modeling looks such as beauty, mommy, product, and older hands. This is just as important as having nice-looking hands. Can you hold an object for an extended period of time without leaning on anything and without shaking? Any movement will translate into blurry pictures, so if you find that you can't keep your hands steady, modeling might not be the best use for them. Shooting TV commercials or ads for your hands can take several hours. A  30 second spot can take upwards of 12 hours to shoot and you have to be ready at all times and prepared to do take after take of small actions. If you want to be a hand model, then you have to prepare to hold your hands in the exact same position for hours on end. This means that you have to deal well with boredom and have really, really steady hands. If you're addicted to caffeine or chocolate, you may have to curb your addiction, because these things will only make your hands shake more. You can even practice holding your hands steady for long periods of time so you'll be more comfortable when the time comes. Patience and the ability to always hit your mark can be the most important thing. Once the camera and lights are set, you have to be able to set the product down in the exact same place over and over.
Have camera-ready hands. Have steady hands. Have patience.