Flyers and posters are effective ways of educating the gathering about waste disposal.
I always stand for zero-waste events (limiting the amount of wastes going to the landfills). It is a big step towards reducing the ecological footprint of events. It doesn’t take much to execute this plan effectively.
Have a clear understanding of how many people you will be providing food for, exactly. Thus, one can cut down on the amount of leftover food waste.
Stick to electronic media for invitations and marketing than relying too much on paper.
Rent a Zero-waste station from your locality for waste management services to provide compost and recycling bins. Renting garbage bins will make your event hassle-free, check this article (http://www.gorillabins.ca/blog/large-event-must-haves-why-renting-a-garbage-bin-will-save-you-a-lot-of-hassle/
Have volunteers stand guard at the waste disposal area to make sure trash goes into the right bin.
Shop compostable, disposable products like cups, utensils, napkins, etc.
A step further offer a carpooling solution among attendees! :-)