Since you will likely be dealing with deeply personal, emotional and financial issues with your mediator, it is important that you feel comfortable with your mediator. It is therefore helpful to take advantage of a free initial consultation if your mediator offers that so that you feel comfortable with your mediator.
Secondly, how much experience does your mediator have? How many divorces or family cases has your mediator mediated? Like anything else, you might be able to find a mediator that charges less and has less experience. In the end you might end spending as much money and/or end up with an agreement that is not comprehensive and has problems due to inexperience. Like in any other area, experience counts.
How well does your mediator know the various courts and the intricacies and local custom of the court you need to file the divorce in? Your mediator should know the courts and their practices. This will assure that your agreement and court papers will be accepted by the court.
What kind of certifications does your mediator have? Although there is no statewide certification for mediators in Massachusetts, there are certifications through statewide and national organizations that attest to the mediator's skill, experience and knowledge. The Massachusetts Council on Family Mediation has a certification system as does the Academy of Professional Family Mediators and the Association of Conflict Resolution. Check to see if your mediator is certified by any of these organizations.
Does your mediator have any reviews or client testimonials? This is no different from researching restaurants, hotels or mechanics. You will learn a lot from client testimonials.
Finally, how committed is your mediator to mediation as a profession? Is this just a sideline or another tool in his or her toolkit or is your mediator committed to the profession? Has your mediator published articles about mediation? Has your mediator spoken at conferences about mediation or mediation related topics? What else does your mediator do to establish a commitment to excellence in the profession.