What are the signs that a speaker is boring?
Fidgeting, yawning, a collective loud sigh/moan when the speaker says "And furthermore...."
If his speech is nonsense:)
They make you fall asleep...
Yawning, txting, sleeping.
When he walks onto the stage and you let out this big yawn. It's a proven warning sign ;)
Don't speak to the air, engage your audience. If your having a good time, they will too.