Can someone go over a rough outline as to how a website design is thought out and then implemented?

As someone who knows primarily the coding side of things, I want to learn a little bit better how to make things that interface well with humans. So I was wondering how people roughly conceive of an idea and figure out what exactly needs to be implemented, as my attempts don't look very well. How do you figure out what details are important? What looks nice? How do you know what emotions are attached to certain colors?