Like others have said, Speech Therapy. Real speech therapy, from someone who specializes in stuttering. It works. As for what to look for: Good speech therapy is only ever roughly 1/3 learning management skills, the other 2/3 is just being able to sit down with your therapist and work through how you feel about your stutter, and yourself because of it. Learning to own it and to be okay with forcibly making space for yourself in conversation when needed is half the battle. That said, if you've reached early adulthood with it, it's not likely to go away. Speech therapy, even good speech therapy, can only help you manage it. That's another sign of a good therapist: they acknowledge this and are prepared to help people who do not want to accept this to do so. A therapist worth their salt will not try to "train it out of you," because they know that's close to impossible, and will only harm your image of your stutter and yourself. The only way it goes away is if it does so on its own. Good luck, man.