Architecture: CSS

There are many right and wrong ways to develop CSS. How do you build a good foundation for your architecture? Music by: Soundshrim, Ambient Background - https://www.jamendo.com/track/1320383/ambient-background?language=en Chris Zabriskie, Candlepower - http://freemusicarchive.org/music/Chris_Zabriskie/Divider/02_-_Candlepower