Understand What You Are Getting Into
The best thing you can do before you install the macOS Big Sur beta is to understand what you are getting into.
This is an early pre-release software update that will not always work. Apple goes through many betas during this process and the first several betas are especially problematic as the test expands to more users.
While you can install the macOS Big Sur beta without joining the developer program, you will still be on the early access version. The Public macOS beta is usually a month later and typically offers 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.
Many third-party apps may not work perfectly on the macOS beta, so if there are apps that you rely on for your job avoid this beta.