Most people know that using the waveform zoom buttons in the toolbar you can zoom waveforms vertically. Since the introduction of clip gain there has been the potential for confusion as there are now two possible reasons why waveform height has changed. Zooming is straightforward but its not at all obvious how to get back to where you started.
To reset your waveforms back to the default level of zoom simply use CMD+Opt+Ctrl+[ on a mac or Ctrl+Alt+Start+[ on a PC. Alternatively you could double-click the Zoom tool to achieve almost the same result. While it does reset waveform zoom, double-clicking the Zoom tool also zooms out horizontally to show your entire timeline.