Read the HTML5 Spec for Web Authors
This is a rather nice concise version of the full-on implementors guide, which can be a bit heavy.
Read the Current CSS Specs
No such "spec for authors" version of the CSS spec. It's not even all in one document :| Still required reading though, especially the stable sections.
THERE IS NO STEP THREE.
But if you really want one, it could be “go make great websites based on what you’ve read”. Alternatively, read Mozilla’s JavaScript Reference. Or if you want to go back to basics, try the HTTP/1.1 Spec, that’s quite interesting.
How to be a better web designer in three easy steps
Three things every person in the web business should do.