My backround includes a lot of experience with the dental profession.
On having white teeth:
Aside from veneers or other cosmetic dentistry, there are two categories of ways to whiten your teeth. One is with powerful whitening agents from your dentist. The other is with less powerful, but more convenient over-the-counter solutions.
For around $200, go to your dentist and have them make bleaching trays for you. They should last many years. Then your dentist will give you some tubes of whitening agent. They look like the stuff in the link BIBLE BELT posted. They are very powerful, and require few applications, but they may make your teeth very sensitive temporarily. You should only need to use these 1-2 times a year.
Now, in between, use things like Listerine whitening, toothpastes that whiten, and (maybe once a quarter) whitening strips to MAINTAIN your whiteness. This will make it so you don't need to use the powerful whitening agents more than once or twice a year. I think a lot of people underestimate how much white teeth enhance your appearance and sex appeal. It's easy to do, and separates you from the crowd.