I'd say, having never really thought about it, you learn quality by coding the same thing repeatedly and optimizing it each time. So you can learn in that way.
Where to find friends who can review my code?
All of my friends don't know anything about programming or they don't code in there spare times like I do.
It is really hard to find someone who can explain what is bad about code design and what should I do about it or what should be "best".
That is when joining a OS project makes same. Then you will have a whole mailing list reviewing your patches, and discussing all kind of architecture decisions.
It is possible to build an app that does exactly what you want and is completely unmaintainable in the future. If you don't know anything about code quality, it is rather hard to pick up on your own. It helps if you have someone more experienced to look at your code and go "No, you're doing it wrong. You don't need to subclass for x, just use y instead."
And having a friendly reviewer is excellent!