Greet EVERYONE, from the people who will repair things, to members of the press, to those who have broken items, to those who just want to observe by watching. The most gratifying phrase you can tell anyone will be "welcome back".
Have a contingency plan ready if the person designated to set up the event can't do so in a timely manner. This plan will be even more important if the designated person will be setting up for the first time. Sometimes those people just plain forgot they were supposed to set up for that day. Anyone who expressed an interest in group by attending an event will have their interest dashed quickly by an unannounced cancellation.
Have another contingency plan ready if your regular venue isn't available for your event, because of natural disaster or plain-old-fashioned miscommunication.
Have your set of tools cover about 80% of the fixes you will encounter. Let your improvisational skills handle the other 20%. Trying for more than 80% will weigh you down and paralyze you into thinking you need a tool on-hand for everything.