Same way they get to Carnegie Hall. Practice.
The canonical punchline is, "Practice, practice, practice!"
<
http://en.wikipedia.org/wiki/Carnegie_Hall#Folklore>
There is a purpose to the repetition.
Specifically, read tutorials, try the examples, create sample projects
for yourself, read books, try the examples, create sample projects for
yourself, engage a study partner, trade examples, create sample
projects for yourselves.
Pick one or two areas to practice at a time until you're comfortable
with them. For example, I spent some time studying and trying JSF
(Java Server Face). I spent some time likewise with JPA (the Java
Persistence API), using as a sample project one where I'd used my own
custom JDBC layer (three different ways) first. Lately I've been
studying Java Enterprise portal application development (and
deployment). I tried a "WeatherMap" example once I figured out how to
install a portal server (OpenPortal, this time). Next it was time to
create my own simple portal app.
If you are just starting out with a programming language or
environment, there are often online tutorials that provide excellent
starting points. For example,
<
http://java.sun.com/developer/onlineTraining/>