One of the most important things in getting runners to sign up is having an easy and seamless registration process. This means offering online registration, which gives the runners the option of getting their paperwork done before the day of the race, usually at a reduced rate. For last-minute entrants, make sure that your entry form is a single page with clearly marked fields. Ask them to write legibly and make sure your registration volunteers read their names back to them to ensure they're accurate. When ordering race bibs and safety pins, always make sure you have more than you need. Also, be sure to instruct runners to wear their numbers on the front so they can easily be recorded as they cross the finish line. Be prepared to hand out snacks at the finish line, too. Runners will be hungry and will need food to regain some energy. Consider asking restaurants or grocery stores to act as sponsor and provide the goodies. All of these registration details ultimately affect the results of the race, so it's important to make sure everything is executed properly. You may also want to hire a person or a company to administer the timing of the race to ensure accurate results.
Overall, the No. 1, most important aspect of the event is safety, and there are many considerations that go into this. The first one is to make sure you have enough water, so take the amount you think you'll need and double it. You'll need ample signage and volunteers to man the course so that the runners stay on course. You must have traffic control to make sure that cars can't enter the course and risk hitting a runner, and you should strongly consider having an EMT or some sort of medical presence on site. If you don't, be sure that your volunteers have clear instructions to call 911 without hesitation if an emergency were to occur. Most races require that you sign a waiver, so you're not responsible for any injuries that may occur. At the end of the day, if everyone crosses the finish line safely, you've hosted a successful event.