You can see available commands with:
./mach -h
./mach <sub-command> -h
Only arguments that need more explanation will be documented here.
Use --pref to enable experimental features like the experimental DOM APIs, JavaScript APIs and CSS properties.
e.g. To enable Web VR and Bluetooth features:
./mach run -d -- --pref dom.webvr.enabled --pref dom.bluetooth.enabled ...
You can find all the available preferences at resources/prefs.json.
Use --devtools 6000 to start the devtools server on port 6000.
e.g.
./mach run -d --devtools=6000 https://servo.org
To connect to the server, follow this guide.