Be sure to arrive early to the venue with your team members and volunteers who should all be wearing distinct clothing, a badge, or something noticeable so that participants can find help if needed. Check the basics like power, water, electronic equipment, etc is in working order.
Walk the Event
Put out welcome banners and other relevant inforormation and, starting with the reception and registration counter, walk through the event checking any important elements on the way - toilets, stands/stalls, PA system, music, refreshments, displays, staging, etc. If you find any problems assign a team member (if available) to address the problem.
Be Available
Be ready to welcome delegates, speakers, guests and ensure they know where they need to be and when (you may have a separate person to do this). When the event is in full swing be available to solve problems and any issues that arrive.
Record and Review
If possible take photos of the event especially sponsors' banners, the event banner, the entrance, receptions, stands, etc, to illustrate press releases and event write ups. If this is an annual event get the feedback from participants, it will help you to improve the next year.
At the end of the day check around the site for to make sure nothing valuable has been left behind, have a general tidy up, remove the banners, tables, etc, and leave the venue.
Job done . . . . well nearly!
Next month - After the Event