Gain staging refers to the process of managing the relative levels – at each stage of the audio signal path – in the mix to prevent introduction of noise and distortion. This can have a profound impact on the quality of your recordings.
Generally, the goal is to keep the signal chain as clean as possible, that is, high above the noise floor without overloading. Proper gain staging is critical in setting the levels to maximize the signal-to-noise ratio of the input signals.
Treat every device in the setup as an opportunity to compound errors. Consider both hardware and software components of this issue (although headroom is not really a problem in the digital world).
So don’t run hot during mixing or the D/A converters will start to introduce clipping and artefacts. Still, you can clip shit, e.g. the drum channel (by doing so you can achieve some effect, some pop). That being said, never let the master fader clip.