Well before the event, it's a good idea to scope out your venue and figure out how everything will be set up. You may need to make additional arrangements to accommodate the floor plan -- extension cords, lighting, etc. And if it's hard to find for you, it'll probably be hard to find for your guests, so be sure to take that into account, too!  If it's up to you, map out where everything will go and when. If there isn't room for it, it needs to go. Talk to the venue's manager about what help they're willing and able to pitch in and if there are any city codes you need to abide by, especially in the case of emergency. Your crews are going to be working hard. In order to show them your appreciation and to keep them on top of their game, make them a kit to give at the top of the event. Bottles of water, granola bars, chocolates, little tokens of appreciation, whatever you see fit. It'll up morale from the get-go, too.  Consider getting them badges or a little party favor to make them feel part of the event and to remember it by. And make sure they stay fed and watered! Always think of your team as resources you want to be able to use in the future. Before the event, it's important to have all your ducks in a row. Be sure to provide clear instructions to your crew on how to get to the site and give them your number or preferably a business card with contacts to call if they need directions. Does anybody have any questions? No? And break!  Make sure everyone is comfortable with their duties. Some people may not be willing to vocalize this, so read them if at all possible. Do they seem sure and confident? If not, reassure them, go over their duties, and ask them a few basic questions. When in doubt, pair them with a more able partner. Your own personal organization is just as important as the event's organization. If you're organized and things go haywire, all can still be fine. But if you're not, hell can break loose. Here's a few ways to prepare yourself:   Make a contact sheet with phone numbers and addresses. The baker thought you were picking up the cake? No problem. Call Ashley who lives nearby -- she can swing by the bakery on her way to the event. Make a checklist. As teams file in, you'll know what goods, what equipment, and what bodies are missing. Prepare invoices and billing as necessary. The more on top of your game you are now, the fewer problems you'll have later. Is it likely there will be frequent artistic changes? Weddings are infamous for clients making last minute design changes so it is wise to recommend to your clients a cut-off date for changes. Usually 1 week before the event is leaving it very close, but it gives the client some flexibility and avoids last minute changes coming too late to be practical or cost effective to implement. If it is simple, subtle or basic changes using already sourced decorations, then it is not unreasonable to accede to change requests. Be as accommodating as possible in what is usually a very emotionally anticipated event.
Get familiar with the venue. Consider making kits for your team. Check in with all teams and outside parties. Prepare a contact list and other paperwork, if necessary. Avoid last-minute changes.