Can porcelain veneers be put on just a few teeth, or do all your teeth need them? I have a few teeth that I'm not happy with, and am thinking about porcelain veneers. I'm worried that those teeth will then look way different from all the rest of my teeth.

Yes. A skilled cosmetic dentist can blend a single veneer into your smile. Don't feel like you need to do your entire smile.
Yes. If only a few teeth are done i would recommend that the same number of veneers be done on the left and right sides so that the result is balanced. It is difficult to match the existing teeth but with effort a nice job can be done. The veneers do not have to be way different than the rest of the teeth.
It . It is almost impossible to exactly match the color of the veneers to natural teeth or existing crowns so most patients are happiest when matching veneers are placed on all the teeth that show when they smile. This can be pricey. You may want to try placing them only on the upper 6 teeth that show the most. You can always add more later if you are unhappy with the match.
Albany, I . Albany, i have done some amazing single veneers when necessary. But, with time even those perfect matches drift from ideal. Usually the opposite/adjacent non-veneered tooth changes shade. In an ideal world veneering all teeth shown in your smile would allow an artistic quality dentist the best opportunity to create a beautiful smile. Unless costs are not a factor, many patients choose to scale back. You should determine what your goals in changing your esthetics are and discuss your treatment options with them in mind. Hope this is helpful, michael i. Wollock, dmd, agd fellow dentistry at suburban square 610-649-0313 www.Dentistryatsuburbansquare.Com.
It . It is not necessary in most situations to require veneers on all visible teeth unless the nature of the problem involves all of those teeth. It is quite possible to conceal the transition between teeth and veneers if the case is designed properly. Each case is different, but again not all cases require all teeth in the "smile zone".