How would a layman know that a particular Reiki Practitioner/Master Teacher is good for h/him?
In the same manner in which one would know if a doctor, lawyer, teacher, or any other professional is honest and reputable; get a referral from someone you know and trust. At the very least, conduct your own interview with the practitioner. Above all, trust your own instincts. You will know if h/she has your best interest at heart and is a “good match” for you.