Research costal breathing. For me personally a lot of it comes when I’m not breathing correctly, deep diaphragmic breathing and one word per breath. Get the relaxed state down, remain eye contact, project your voice, wrap a belt just below your chest (above ribs) and if you take a deep breath you should feel the belt tighten. This is a good physical indication that you’re good to exhale and say the words you want to say. Good luck.