I've been to one when I was around 12-13 years old for a few sessions. So I only have experience with what I did. But a large part of it was practicing how to speak slower and start out my sentences slower and then start talking at a normal pace. This was mainly because I tend to have trouble start out sentences while speaking, and not always as much once I'm already mid sentence. But we also practiced on certain sounds that I would frequently mess up on and get stuck. I cant remember everything but those were things I do still remember. Hope this helped a bit.