Understand What You Are Getting Into
The biggest thing you can do before you install the macOS 10.15 beta is to understand what you are signing up for. This is pre-release software that will not always work. Apple will go through many betas during the next few months and the first few betas will be especially problematic as the test expands to more users.
While you can install the macOS 10.15 beta without joining the developer program, you will still be on the early access version. The Public macOS Catalina beta is now out and should offer smoother performance.
It's not just system issues that may pop up while you use the beta. You can expect to see battery life issues, potential connectivity issues with WiFi and Bluetooth and other problems. Here's a rundown of macOS Catalina problems.
Many third-party apps may not work perfectly on the macOS Catalina beta, so if there are apps that you rely on for your job avoid this beta.