A good therapist is someone who has done extensive training in a relevant field and has counselled for a number of years. You might see a number of different acronyms indicating what kind of education a professional has gone through in order to become proficient in counselling.

A therapist and counsellor mean the same thing and are often social workers or psychotherapists. A psychiatrist has a medical background and is able to diagnose mental illness and prescribe medication. (It’s pretty rare that they offer counselling). A psychologist is someone who conducts research, conducts assessments, and/or offers counselling services, as well.

Keep in mind that these credentials are the minimum of what you need to achieve in order to be a therapist; therefore, I recommend that you find someone who has continued their education and learnt more about specific counselling theories. After all, the more strategies a therapist has in their toolbox, the more they can draw from when they are working with you to develop a therapeutic plan to meet your goals. 

That being said, you can have the most skilled therapist in town, but if you don't actually want to talk to them, then those credentials won't do you (or your goals) much good. Because counselling involves being vulnerable and taking emotional risks, it is important that you feel comfortable and safe with your therapist. Ideally, you will feel heard by your therapist and are someone whom you can trust. The best way to discover if you have found the right fit is to meet the counsellor directly. 

If you want more information on what to look for in an effective therapist, check out this link.
If you are new to therapy, check out “6 Things a Therapist Wants You to Know.”