I hope you did well!
I would have reccomended getting their early-a ways before the start of the event so that you're not taking up someones time that is intended to be used elsewhere-they will be nice, but you must realize they will be busy-it's stressfull for them, too. Even if you show up early just out of professionalism it will earn you a little more respect, or in other words, you'll score more brownie points. Not to mention the fantastic lighting available early in the morning.
When I cover an event I like to get there a couple of hours prior to the start-IE bike race weekend-if the track is hot at 8 I'm there no later than 6:30. Meet with whoever is in charge, or in charge of media depending on the size of the event. If there are marshalls that I don't allready know, I'll try to take a second and intorduce myself, let them know where I'll be shooting from and 'ask' them if they feel o.k. with that-it gives them the feeling they're in control, and I've never had one give me any grief yet. Find out where you are and aren't allowed and stick to it like it's the most important thing in the world. Find out where to go sign your waiver BEFORE you get into location and start shooting-dont make them come find you(waivers are pretty much a given as covered by kenny g).
Finally-once you've taken care of all the formalities-clear off and give them space to do their thing smoothly. Take a walk around and try and figure out some shots beforehand. Especially if the venue is new to you.
Finally if you have the access, mill about the subjects and shoot them getting prepared. This will add depth to your coverage. ie. when I shoot a race and I know there will be a podium presantation afterwards, I shoot the victory lap, and then hustle my butt off to the other end of the track to cover the podium...the clients will thank you for it.
Most importantly-carry yourself in a professional manner at all times. I'm not sure what your full time job is, but if you're acting as a member of the media for the day-treat it as you would a job. You're not only representing your client, but you're representing YOURSELF. Organizers/media relations folks have INCREDIBLE memories. You wouldn't believe the things they'll remember about you, be it good or bad.
BE HONEST with the folks in charge. Introduce yourself and make sure you mention this is your first time shooting this type of event, don't try to 'save face' by acting like you know everything you need to know. Most likely they'll figure that out for themselves anyway.
Be PREPARED. Bring lots of water, lots of kleenex and energy bars etc. A cooler in the car with a little ice is a good idea also-especially if you're able to scoot back to your car from where the event is being held.
ALSO! Enjoy yourself! Have a blast, and do it safely!
Canon EOS Digital Gear, Light and Luck.
Not always in that order.