Finding a Botox Injector - What Sort of Credentials Should I Look For?

The physician's on this site are probably a reasonable starting point. Beyond the board certification and the number of years in practice, you may want to consider the training that the injector has undertaken. Does he/she have ongoing credits for injection training, do they attend industry workshops to keep up with best practices?
These are questions you can ask in a first consultation and we suggest you attend at least two or three in that 10 day period before making a decision.
The best way to choose a practitioner is with a referral from a friend. Bit short of that, use some of the tips above as a starting point.

Botox treatment is an art and a science. The provider should be very knowledgeable about the anatomy, the chemistry and side effects. The artistry comes from both experience and an innate sense of observational skills and an interest in the physician or provider to learn constantly and improve on the outcome. There are nurses and physician assistants who perform these treatments but they should be under the supervision of a licensed physician. Dermatologists have been performing Botox for many years as have Plastic surgeons. Today, you hear of gynecologists and dentists performing the treatment as well. It is very important that the practice uses aseptic (clean) technique so there is no cross-contamination. A board certified dermatologist or plastic surgeon is your best bet, but then it is up to the experience of that provider. I have been performing Botox injections for 15 years and still improve my results continually. In addition, we have learned of new techniques and applications with Botox. You can check with the American Society for Dermatologic Surgeons to find a member close to you, or the American Society for Plastic Surgeons. Furthermore, if you are lucky to know of an individual in that area who has had Botox done, their comments about the physician performing the treatment can be very helpful to you.

Liz,
First of all, many types of doctors are now doing botox injections (including family practice, OB GYN, anesthesia, etc.) that are not formally trained to do the injections (they may have learned it in a weekend course).
Also, many health spas and medi-spas may have individuals (often not doctors) that are also doing Botox injections in a casual environment of a spa rather than in a medical office.
Finally, some doctors utilize "nurse injectors" that actually do the injections for the physician, even though the patient may have called the "named doctor" and thought he/she may be doing the injections.
My advice is really pretty simple...See a board certified plastic surgeon, ophthalmologist, dermatologist or facial plastic surgeon with experience...those are really the only 4 specialities that are formally trained to do botox injections during their medical training. They also have then most experience. I would also see a doctor, rather than a nurse injector, to do the injections.
If the doctor you see uses the term "cosmetic" doctor or something similar, ask them what specialty are they formally trained in as far as the residency that they did, and then ask if they are board certified. That is a pretty good way to sort out the quality, training, and expertise of the doctor you are considering.
I hope this helps.