Find the janitor and get some chalk. Find where the last turkey who used the pointer misplaced it. You get the idea. Start out small and simple, then-but plan on metamorphosing into a Major Event as soon as possible. As it was, he got the crown jewels.
Planning starts many months in advance.
Films and auditoria may require six to nine months' lead time to obtain. I solved that problem at Michigan only by switching to Friday evenings, when there are no classes. You learn how by observing good and bad lecturers, then adapting what you see to your particular style, knowledge, and interests. If someone asks a question and the audience laughs, you have a crisis. Get across right now that no one need fear to ask any questions, or you've lost them.