When you're confident you can drive 10 laps without mistake, restart the python mange.py process to create a new tub session. Press Start Recording if using web controller. The joystick will auto record with any non-zero throttle.
If you crash or run off the track press Stop Car immediately to stop recording. If you are using a joystick tap the Triangle button to erase the last 5 seconds of records.
After you've collected 10-20 laps of good data (5-20k images) you can stop your car with Ctrl-c in the ssh session for your car.
The data you've collected is in the data folder in the most recent tub folder.