RB Whitaker's tutorials are a pretty good place to start. Classes are covered in #15 and onwards, but it's not a bad idea to go back a few more and cover the basics.

You are going to miss some things, eventually. It's inevitable with a non-standardized education, and the more thorough a resource is, the more people tend to gloss over it. The more concise it is, the more likely something gets left out.

Any time you run into trouble, try going back over the related sections in your books or tutorials to see if anything jumps out that you might have missed the first time.