Note: these rules are not canonical, but they tend to work well in play. Feel free to adjust them as needed.
The presenter cannot see the slides before presenting.
The presenter delivers each slide in succession without skipping slides or going back.
The presentation ends when all slides are presented, or after 6 minutes (whichever comes first).
Games can judged by a panel or by popular vote. One common way to measure popularity is to have the audience applaude for each presentor once all the presentations are done; the name that garners the loudest applause is then proclaimed the winner.
Content and Credibility (did it make any sense)
Poise and Gestures (were they comfortable)
Flow (minimal pauses and stammering)
Audience Response (was there any)
Getting through all the slides!
Tips for Presenters
Try to tie the slides together into a cohesive theme.
Relax. Don't take yourself too seriously.
Download a pack of slides to get your party started.