It is really tough attracting attendees this fall; most shows are down 10 to 30% and international attendance is in the tank. Here are some suggestions for those shows being held in the next six months:
Renegotiate your room rates and then promote this to your prospects ("We have gotten you very affordable hotel rates").
Ditto for air fares. Research the new, lower fares from key cities to your destination and make sure your prospects know. Personal example—Hartford to Chicago is now only $212 roundtrip so I can't afford not to go to IAEM in December.
For international prospects, send them a personal and targeted message that says travel to/within U.S. is safe (and explain why). Also tell them exactly what steps you are taking to make your show secure.
Offer a big discount, such as bring two colleagues free to the conference (3 for 1).
FLASH: In light of the anthrax scare, follow this guideline for any enveloped promotion package you send: Put your show logo/street address/URL clearly on the front (upper left) of the envelope. DO NOT send a plain envelope and DO NOT enclose anything but paper. In fact, consider moving completely to self-mailer brochures and post cards.