Counselors on The National Registry of Marriage Friendly Therapistssm should be able and willing to answer the following.
If the marriage counselor is self-taught or only workshop-trained, and can't point to significant education in this work, then consider going elsewhere.
Marriage therapy or counseling is one of the most challenging forms of therapy which means it can be risky for your marriage if you are not with someone experienced. Marriage Friendly Therapists exists because not only were couples coming to Kathleen Wenger, but therapists themselves coming for their own therapy, complaining of their awful experiences. And when they were asked where they could go for marriage therapy, Kathleen did not have a good source to refer them. This is why the Registry was created.
What many couples are not aware of is that you can practice marriage therapy without any experience, training, or coursework. Any counseling license (and there are many) allows anyone to see couples even if they have never seen a couple before or read anything about couples therapy. Your marriage needs an experienced therapist who also believes your marriage is worth saving.