There are all sorts of reiki healers to choose from, with all sorts of training and background. With over 140 different styles of reiki to choose from the options are huge, but what any reiki healer should have is an understanding of the skill that they can transmit to you.
Reiki healers work with patients to figure out the best treatment, paying due regard to the patient's symptoms, medical condition, and medications they may be taking.
Choosing a practitioner who is right for you starts when you call them up. It's important to ask any questions you may have about how they work - this ensures that they know what they are talking about, and that you are comfortable putting your treatment in their hands.
You will want to know about their qualifications - what training have they had, and whether they belong to an accredited association. Experience is good, but the bottom line is whether you feel relaxed and comfortable with them.
They will want to know what conditions you have - some practitioners specialise in certain conditions, or are unwilling to work with certain areas. All practitioners will be able to offer you a relaxing treatment, but if you have more specific needs, it is important to talk about that up front.
The practitioner should also discuss any potential contraindications that may limit or prevent treatment - for example, if you have a pacemaker you should not have this treatment as the work with the electromagnetic field can potentially alter the speed of the pacemaker.