1. Someone asks me a question that I don’t know the answer to
To prevent: Learn more your topic, discuss with expert before you present it. If it still happen, it’s OK to tell “Please inform me your email. I will answer your question later”. Do not afraid to say “I don’t know”. It is really better than your “doremi” answer.
2. I forget what I’m going to say
Be disciplined about going through the speech / presentation as many times as it takes. Some people can go through their talking points in 3 or 4 times, and be ready to rock. Other people need 10 times as many run throughs. Know what your category is. And don’t judge yourself, just schedule your time to practice it.