The best thing to do is promote your hunt like anything else. Use social media, print materials, websites and any other resources you have to tell people about the hunt. If possible it is often best to tell people about the hunt in advance to get some buzz going and then remind people right before the hunt starts. It's also a great way to tell them how to join the hunt prior to the start date/time, which will give them the opportunity to download the app and join the hunt prior to the start. It is also a great idea to keep promoting your hunt as it is going on. Share some photos from your hunt with your social media, etc to attract new people. If you have any questions on the steps you should promote for someone to join your hunt, feel free to take a look at how we promote our demo hunt.
Be sure to check out our Promoting Your Program guide for more information and suggestions.