So many random thoughts. Lots of good suggestions already here.
Please try to minimize the number of sharp turns in the final 200m of a race of any distance. I know that some are unavoidable, but when the finish line is following a 90 degree turn with just 30 m remaining in at the end of a race it’s annoying, and potentially dangerous especially if the chute is narrow and the field is large.
If it’s a large race, sign up high school or college aged volunteers to help people toss their waste into the correct receptacles, and actually have trash, recycling, and compost options (and more than one bin). I ran a half marathon once with thousands of runners that only netted one bag of trash because the waste generated was either recyclable or compostable, they had enough bags and bins, and volunteer minders helpfully and assertively making sure the waste goes in the right place. Tired of seeing large public parks essentially trashed because there are two garbage bins and they’re full before the race starts, with no city clean up until Monday.
Ditto mailing out the bibs/packets in advance (if it’s a big race; if it’s a small local thing that may be prohibitively expensive).
Don’t make runners wait for the gun while thanking every local politician and community leader, it’s nice, but you could do that while people are milling about, too. I disagree about the sponsored T-shirts. If you’re going to have sponsored shirts, put everyone’s name there so you don’t waste time in the heat or the cold rattling off names. It’s amazing road races have sponsors. Don’t create unnecessary swag, but I don’t begrudge having a whole flight of sponsors or local officials listen on the back.
If you’re going to have a sound system to make announcements, rent one that works and place speakers near where you need people to stand. Worse than the lengthy announcements are the lengthy announcements with directions that people can’t actually hear.
Please mark the course well or station volunteers. I, and several others, once ran into a different city because of poor markings. On the flip side, I ran my hometown 5K a ton of times when I was in HS and college before I moved away. The course was only nominally marked, but it was the same course for YEARS and everyone who ran it knew that. So maybe the guidance is also to know the audience of runners.
Awards for top finishers and age groups don’t have to be a medal. One trail race I ran gave out pint glasses with the name and logo of the trail race (both happened to be very good). One road race gave a small towel to everyone. It seemed silly at the time, but it’s been useful to have and it’s fun to recall the race whenever I use it and I’ve had it for more than a decade.
It’s very nice to hand out Gatorade at the end of the race. But if the color of Gatorade chosen matches the unusual colors of the road race logo/theme, but the flavor tastes weird, and it’s a hot summer race, and the Gatorade is sitting out in the sun, it can be pretty gross. Sometimes over commitment to the theme doesn’t help.
Selling merchandise is a great idea. Some people want the stuff and some people don’t, and if it’s not bundled into the cost of entry, people can choose.
I love the idea of discounted entry or guaranteed entry or instant entry (or something) into next year's race.
Know if your race is a small, local thing that should be low-key with minimal frills or a big, regional thing that needs to go all out. I love running local Kiwanis Club 5Ks and big races that get coverage by Letsrun.com (not of me! Coverage of the fast people), but I think it’s the mid-range races that need to think really carefully how to balance budget with quality of experience, and in fairness that can be hard.