When photographing an event it is easy to get caught up in all the big things that are happening, and that is a dangerous trap to fall into. While event organizers will want those big moments captured, you'll also find that they appreciate it when you make images of the small thing too. So don't forget to put your creative thinking cap on when you are out working.
At a charity event for example, that could mean photos of sponsor representatives, sponsor products, event posters and the location. Try to capture the mood, the place and the things that are part of the event, rather than just the highlights.