That's a really good question. First of all you need to be confident in what you want to say and feel safe to express yourself. It does take a lot of practice and you will get burned but the more you speak up and express yourself, the better everything gets. sitting in silence just makes things worse, especially if you want to speak. stutter and let them know what's happening and contribute when you have something to say. it's not the answer people want to hear but it's the way forward ! :)