More often than you'd expect, I am asked how to get started developing for Android. Just saying "http://developer.android.com/" is a bit too trite, so here it is in a bit more detail.

1. It is pretty much essential to know the syntax of the Java programming language. Knowing how to read and write XML documents is only slightly less important. You won't go far in Android without knowing these two basic technologies.

2. Subscribe to android-developers and Stack Overflow. Seriously.

3. Install the Android SDK. Make sure you have all the prerequisites on your computer before you install. Create and start up an AVD.

4. Read everything in the Dev Guide under the heading "Android Basics".

5. Read and complete all the Tutorials.

6. Create some new Android projects based on the samples and start experimenting.

There's obviously a lot more: Useful Android-oriented books, blogs and tutorials abound. The above makes a good foundation to get you started.