Don't skimp on the small stuff when you're producing an event. People will always expect certain things, and if they've paid to be there, they have a right to expect those things.
#59: If you have an event or seminar, provide beverages, a coat rack, and snacks.
#60: Validate parking if free parking isn't available. If you can't validate parking, work out an arrangement with your venue to include parking in the price of admission.
#61: If parking is still an issue, offer a shuttle service to and from the event.
#62: Make it easy for people to register; offer online registration from your website. This method should collect their contact information, accept and process credit cards, and send attendees their confirmation automatically. (There are services available for accomplishing this if you're not sure how to do it yourself.)
#63: Make sure the bathrooms are clean and tended to regularly.
#64: Ensure there are enough trash receptacles and that they are emptied periodically (before they're overflowing).
#65: Work with your local chamber of commerce, business associations, and networking organizations to promote your event to their members.
#66: Offer meals during an all-day event. This serves two purposes. First, you'll have less stragglers wandering back in from lunch after the event has picked back up. Second, by giving attendees a reason to sit at their table, they network with each other over lunch, bonding with each other (and your brand) in the process.