It helps to know what you want from MC. Tell that to prospective MCs and see how they respond.
It may be that what you really want is IC, BTW.
I'd want someone experienced in helping couples heal from infidelity and in helping couples R. Personally, I don't like homework, I don't like structure, and I do like confrontation. That meant I looked for an MC who didn't assign homework, didn't impose a lot of structure, and who confronts effectively, but not noisily or intensely - we get intense during the sessions, but the MC stays calm.
I guess I also like compassion and support, even it it's 'tough love' sometimes.