I attended both of these talks and found them very enlightening. My team hired a CSS expert to do some part time implementation work and evaluate our practices. I was pleasantly surprised when his analysis of our codebase was very positive.

To me, the key is to think of everything in your app as a component. You should be able to drop the component into more or less any context and it should 'just work'. Following the ideas in the videos will help you accomplish that on the CSS side.

CSS is a Mess - Jonathan Snooks (ex-Lead Frontend Developer Shopify) https://www.youtube.com/watch?v=fAcW-wOFYjw

CSS for Engineers - Keith J Grant (NYSE Engineer, author of CSS in Depth) https://www.youtube.com/watch?v=J-9Tn6AetYA

I really like http://cssreference.io

They have a visual guide which shows you what it looks like along with code on side.

You may want to look into Sass (SCSS). It makes your code reusable and extendable via variables, mixins, loops, if/else statements- its quite robust.

Another suggestion, such as SMACSS is BEM (my personal favorite), as it flattens out your styling to prevent over specificity and makes everything clean and neat. (Check it out here: http://getbem.com/)

Ultimately though, what I've found reduces messes is to think of the end product before beginning. If you have the luxury of starting with a fresh codebase, think of the end product and its styling before starting- much like you would with any other set of features in any other language.

If you're walking in to legacy code, try to avoid the "one-offs". Sure, they solve the problem now, but its making a mess for future you to clean up as well as being a potential code smell. Leave your code a little better than when you came in and you'll be thanking yourself later.

Good luck!

I think the SMACSS doc is worth a read:

https://smacss.com/book/

+1 on SMACSS. It seems like you are comfortable with CSS but unsure of the architecture and scaling behind its usage.

One trick I just learned is you can combine classes - when setting class in a property put in multiple classes by separating the names with a space. i.e. <div class="manny moe jack">web stuff</div> Now you can pull apart the unique bits from the reusable ones.

Other than that a lot of my CSS cleanup happens in refactoring the layout

npm.im/styled-components