The keys to success:
Assemble camera and audio equipment ahead of time or arrive early enough to prepare on site.
Get as much information from the organizers as possible, if you have a clear idea on what they want the final edit to look like then you have a notion as to what you will need to film.
Take help, a second pair of hands is most likely necessary and a third will just be helpful. Depending on the shoot investing on a third person may be useful.
Be mindful and accommodating to the folks paying but use your experience on the field to hash out bad ideas, do whats necessary to deliver the best possible product. That may include steering away from bad ideas.
Even though you are not following a script and dealing with a multitude of variables that come with a live event I would suggest to still have a patron or structure to the shoot. Organize yourself, have things in order for example: if shooting interviews, b-roll, product shots, and arial footage you must set up the filming in a way that makes since logistically, the trick is to be efficient so we can cover as much ground and film as much coverage. Be aware somethings will be out of your control like natural light, the disposition of the interviewees, and an assortment of other clogs that rear their heads during video shoots, which brings me right to my next point.
Have a plan B for everything. Don't be negative but expect things to fail as initially planned. If you do this you will have a plan B in place to take over. There is nothing more stressful than having an unexpected problem on set. It is a great practice to analyze everything that could potentially go wrong and make adjustments before it happens, this will keep you prepared when the pressure is on and camera's are rolling.
Those are some basic but often overlooked tips which produce good results. Video production can be a rough field, throughout all its stages it keeps you on your toes but keep with it and always remain a student to the craft.