First, you need to decide whether you want to use 2D graphics or 3D graphics.
If you wish to use the former, you have two options:
1) Canvas drawing
2) OpenGL ES
Option 1 is fairly strait-forward and can easily be "learned" by browsing through the android SDK documentation and playing around with the various classes. There are also many tutorials and samples on the android developer's page.
Option 2 is much more complicated, but is also MUCH more powerful. Although all of the classes can also be found in the android SDK documentation, I HIGHLY recommend buying a book on OpenGL (Although Android uses OpenGL ES, it is very similar and, if you know how to use OpenGL, you can adapt to the more dumbed down OpenGL ES much more easily). I always reccomend the OpenGL Super Bible (4th edition).
It can be found here:http://www.amazon.com/OpenGL-SuperBible ... 381&sr=8-2
If you are wishing to use 3D graphics, then your only option is OpenGL ES. In this case, just follow the recommendations above.