Personally i think you should start off with planning, planning ahead. The main issue from your example is the 400 people & the 10 hour lin-up. I suppose like almost any other project you need to be prepared weeks maybe months before the actual date its supposed to take place. Plotting out a weekly timeline could be a good start and setting goals & milestones to achieve every week or so could be of big help.
U may also want to invest time in a plan of action (Action Plan). In other words a description of what needs to be done, when and by whom to achieve the results called for by one or more objectives. It contains task assignments, schedules, resource allocation and evaluation criteria. May be a simpler version of a project plan. So an action plan is a step-by-step plan of action and schedule for correcting a process or a quality issue.
Next and most importantly, the financial/budget plan. How will the project be financed. Will there be/is there a budget? Estimated costs etc etc
The last step is an evaluation on how everything was performed & if everything whent accordingly.
This is just a rough lay-out and how I would try to tackle this project. Especially a project consisting of 400 +- guests. Preparation is key in this case.