Drown yourself in code (writing and reading) and make things. Even if they are simple, or insecure, or very, very inefficient. Just make them. That experience alone will help you get better.
To more specifically answer your question - find something that's bothering you, and make a web-app that tries to fix it.
To more specifically answer your question - find something that's bothering you, and make a web-app that tries to fix it.