First of all, set aside the thinking that there is one best practitioner. Thinking there is a "best doctor", "Best acupuncturist", "best massage therapist", "best reflexologist" is not helpful. It's actually misleading. Many professionals are well trained and experienced, and practice with integrity. The question, instead, should be:
Who best suits my unique needs?
The answer to this is often simply the practitioner you feel most drawn to from among those who meet your criteria.
When possible, it's an advantage to choose a practitioner close at hand. You won't want to go out of your way, on a regular basis.
It is also reasonable to have a brief phone conversation with a practitioner before booking an appointment to ask about their training and to get a sense of their personality!
There are many fine Reflexologists who practice diligently, and have a deep mature relationship with Reflexology.
As you evaluate the information you've gathered, reflect on your own values. Some people gravitate to the practitioner that has the most diplomas, citations or press clippings. Others value clinical manner as highly as training, or the practitioner who is giving reflexology sessions several times a week and has a close and meaningful connection with the treatment and their clients.
Once you have gathered the information you need, go on the decision of your 'gut'. You may be lucky enough to find several competent practitioners.
Go with the one you like the best, the one with whom you feel most at ease.