Developer mode and USB debugging. On each phone, tap Settings → About phone → Build number seven times, then enable USB debugging under Developer options. Accept the RSA prompt with "Always allow from this computer" checked, or DeviceSource won't be able to use the device.
Keep the screen awake. Enable Developer options → Stay awake so the screen never sleeps while charging, and set the screen lock to None. A locked or sleeping screen is the most common cause of flaky UI tests. From the host: adb shell svc power stayon usb
Wi-Fi. SAIR only needs USB, so Wi-Fi is up to you. Leave phones connected if your tests need the network; if your tests toggle connectivity themselves, consider leaving Wi-Fi off between runs so each job starts from a known state. Shared devices can be used by other SAIR users, so avoid joining them to networks you don't want reachable from someone else's test.
Reserve a phone for local work. Debugging on one of the bench phones? Hit Reserve on its device page and CI leaves it alone until you click Release to CI. No config change or restart on the host.
One bench, two accounts. To let another SAIR account (say, your company's) run CI on your phones with its own queue, logs and billing, list its API key in SAIR_GUEST_API_KEYS on your Proxy. The phones stay private, and your own jobs still go first.