Most important thing is to stay safe.
Don't be right on a wheel as you hit a corner - if he slows you have a good chance of going into the back of him.
Don't do anything sudden, like braking or switching your line.
Pick someone big who looks like they know what they're doing, follow the wheel.
If you get too close to the front, you'll get involved in the through-and-off line. Don't worry about that but go through smoothly without sprinting or slowing.
If you're there at the end, sprint. But don't sit up if you blow, keep going or someone will go in the back of you. Don't, really don't, switch in the sprint; hold your line.
If you're there and don't want to sprint - I can understand that, it's dangerous! - then attack with 800 yards to go. Eyeballs out, don't look round, don't stop. If someone catches your wheel, fair enough, it's your first race. But if you get a gap, you've a chance. Either way, flat out to the line.
If, as is in fairness much more likely, you get shot out of the back, don't take it to heart. Eddy Merckx didn't win his first race.
Be safe, have fun. Let us know how it goes?