Did you know that you can reset any individual sliders in the Develop module by double-clicking on the slider name (for example, Exposure)?
I knew this tip, but I just recently learned another tip for resetting groups of sliders in the Basic Panel, from David Julian:
When you hold down the Alt/Opt key, the word Tone becomes a Reset Tone button. Click on this to reset all the tone sliders (In Lightroom 4: Exposure, Contrast, Highlights, Shadows, Whites, Blacks.) Likewise, Presence becomes a Reset Presence button to reset Clarity, Vibrance, and Saturation.
I always wonder if I am the last to discover these tips — thanks, David!