If you are new to Java, you may want to get an introductory book on Java, or try out some of the many tutorials on the web. As for Android itself, I started with "Beginning Android" and "Pro Android" from APress.
For me, I find that the best way to learn a new technology is to go through the first few chapters of a book like the ones mentioned above to get the basics, and then just start building a simple (but not trivial) app. When I run into something I can't do, I lookup that topic in the books I have, or search Stackoverflow or other online references for examples of how to do it. Over the course of a few months, you'll learn how to do most things.