Haven’t gotten married yet, but my two cents as someone without a DOE coordinator (unless you count me :P)
–Checklists. More checklists. Add a few more checklists to be on the safe side. Your head will be anywhere but on things like “where are the reception flowers?” “Has the cake arrived?” but someone has to take care of those things. I even have a checklist for the items that will be in the clutch I’ll carry to the reception. It sounds OCD, I know, but it’ll be a lifesaver. Do I really want to find out after I’ve destroyed my nylons with a fingernail that I don’t have another pair closer than our car? No. Ditto that I need a handkerchief/lipstick/nail file/whatever.
–Similarly, timelines. I’m lucky in that I’ll have the whole week before the wedding off. I already have a timeline for that week, down to what I’m doing during a given hour block on certain days. (Do bear in mind, though, that I’m DIYing the wedding and groom’s cakes, the flowers, and the decorations, plus I’m moving most of my stuff to our new, four-hours-away house the weekend before, so I probably need to be more obsessively organized than perhaps the average bride.)
–Communicate. Do not assume that anyone, from your maid of honor to the celebrant to, yes, your fiance, knows what you’re thinking. You might think she’s supposed to help you with setup all day. She might be thinking she’s spending three hours that afternoon at the spa. Etc. Ask the maids to help with things that they’re good at, and when other friends say “can I help with anything?”…take them up on it. Really. Then write it down. Remind them a week or so before.
–Take plenty of time for YOU that day. Remember to eat breakfast and lunch before an evening ceremony, and make it something balanced with protein. Drink plenty of water. If you find yourself thinking “I can’t pee right now, I’m too busy” you need to delegate, and you probably can’t delegate peeing, mkay? Build in more time than you think you’ll need for hair and makeup. I’m DIYing mine. For a 4:30 ceremony, I’ll be getting to the location at 3:00. I’ve never taken more than 45 minutes to do my hair and makeup, and the “45” quote was probably for either a recital or a show. I know I’ll be nervous, and I might have to redo my makeup a few times before it’s done. That’s fine. What wouldn’t be fine is having my face an inch deep in cold cream at 4:25. When I’m short on time, I’m stressed. Stressed is not a part of my dream wedding day, thankyouverymuch.
–As a PP said, find someone who’s very competent and very tactful and have her take charge of Getting Things Done. Give her a copy of the timeline, everyone’s cell phone numbers, and the checklists. She will save your life today. Remember to send her chocolate or whatever her favorite treat is afterwards. Let her handle the stress, and if the car blows up/the wedding ring gets stolen/the reception venue tells her when she gets there that oh, oops, we double-booked and we’re bumping you…she can handle the worst of it and tell you about it calmly and non-dramatically.