Great post. I always had a problem with presentations when I knew what I would gonna say. Because then I would know all the "difficult" words and that got me worried, and I blocked more. But as the presentations got more advanced (e.g. in university, defense of thesis etc) I noticed that it was hold back, and not by the blocks, but because I didn't know how to phrase and structure my thoughts because I avoided thinking about the presentation too much. So I prepared better, which helped me and made me more calm. They key to fluent speaking is calmness and confidence...when I am talking about something I really know about, I am so confident and it is easy for me to talk, even in public. But if I am not in the right mood (you know, bad speaking days) and feel unsure about the topic, I get a lot of blocks. But I always handle them like in a normal conversation...just try the word again, calmly. Also it is training. Now I have no problems with presentation at all, even in english (I'm native german) because I did a lot of presentations over the last 3-4 semesters..