To a large extent sustainable meetings are the direct responsibility of local hospitality communities. Government is a partner, however, and can provide programs that encourage the development of greener meeting destinations. This is particularly the case for cities that have government managed convention facilities.
Some tools and examples of best practices I've recently come across:
Purchasing policies: Executive Order 08 -02 requires that all city departments in San Francisco - including the Moscone Convention Center - procure products that enhance recycling and resource conservation. This includes mandating the purchase of 100% post consumer recycled content paper and green products that have been approved by the Mayor's Office.
Product bans: From plastic bags to bottle water and polystyrene, municipalities are experimenting with product bans that reduce environmental impacts. Examples include London, Ontario's recent bottled water ban in city facilities - including the convention centre. A trailblazer of a green city, Portland, Oregon banned polystyrene 18 years ago!
Transit initiatives: Yet another innovative example of sustainable living - Portland's Fareless Square. Fareless Square is a transit initiative that includes the downtown and convention neighbourhoods of the city, where passengers can ride the MAX train line for free!
Green building initiatives: Last year the City of Chicago announced a Green Roof Grant Program, designed to help residents and businesses save energy and maintenance costs by creating green rooftops.