CSS is a dark art. That’s about the best you can say about it.
To be honest CSS is a real drag. It destroys your mood and saps your confidence. Things that seem simple just aren’t. It takes way too long to get it right. If you haven’t been frustrated or annoyed with it, you haven’t really tried it.
Still, there are a few ways to make it easier. Your best chance is to develop a methodical approach, otherwise you’ll quickly find yourself chasing your tail like a neurotic puppy.
Next, find some tutorials and free online classes to get your feet wet. I recommend Codecademy because it helped me immensely and you can do a lot for free. Others include webplatform.org and w3schools.
Before writing CSS be sure to check your ego at the door. Some of the best CSS designers I’ve ever met come across as arrogant to the point of ridiculous, but most likely they are over-compensating for the devastating damage done to their egos while they were still struggling to learn it.
CSS starts out feeling rather easy. Then you’re likely to get reckless and wonder why you’re having so many problems. Until you adopt the right tools and approach, CSS just makes you feel stupid, like a cat trying to solve the Rubik’s cube.
Here is a long list of resources for learning and referencing CSS: