Decorations are a major contributor to waste. The are often produced for one-off needs and not allowing for reuse at other events. Decorations should be sourced with the intention of future reuse. For example, if the event has sponsorship and event banners, keep these and the dates & sponsors on separate panels so as dates & sponsors may change every year, the event can still reuse these banners.
Also consider using reclaimed materials when decorating an event. Source a range of reclaimed materials such as timber, foam, fabrics, metal, paper, glass and cardboard. Also consider if decor can be reused, where it can be stored and how easily it can be disassembled / reassembled.
Make sure you also encourage these tips to others also working at the event including contractors and exhibitors.