Line up in the coral depending on how fast of a runner you are, even if the race organizers don't do this for you. Fast in front, slow in back, walkers behind them.
Everyone starts out fast, because of adrenaline - remember to "run your race" even if this means you must slow down to keep running. No one is looking at you, no one is judging you - you do you, and don't worry about anyone else. If you have to stop to walk for a couple seconds, hundredths of a mile, or half the darn race - you do you.
I have yet to be the last one finishing, and I'm a s.l.o.w. runner
Have fun, good luck and enjoy, take a moment or two to soak it all in.