Side-chain compression is most commonly used on the bass track to allow the kick to cut through the mix, by compressing (lowering the volume) of the bass, whenever the kick plays. This creates a ‘pumping’ effect, associated with a lot of dance tracks.
Here’s how you create this effect:
Put a compressor on the bass track, and click the side-chain button. Select the kick from your drum track as the source.
Turn the compressor’s ratio all the way up, and pull the threshold down to taste.
A fast attack and quick release will make the effect even more aggressive.
You can soften the effect by adding adding some dry signal (turn down dry/wet knob), or backing off the threshold and ratio.
Side-chaining can also be applied to all other parts of the track. It can also be used in other creative ways by selecting a source other than the kick to side-chain. The best way is to experiment and surprise yourself.