I have started an Android game designing group with my friends. Since I'm piss poor in coding, I think perhaps I could contribute more in graphics design. However I have pretty much no knowledge in computer graphics, anyone with related knowledge can give me an idea where should I start? Photoshop? 3D Max? Maya? I'm an pencil drawing guy, perhaps I should get myself a tablet? Anyone know how are graphics incorporated with the codes? C++ or Java? What should I cater with while I draw?

For games Adobe Flash Professional CS5 is good for graphics (Vector graphics software). However I am only a beginner with it, but I started making graphics with Adobe Fireworks CS5 and I recommend it for beginners, it has quite a lot of features (not as much as Photoshop though) and is accessible and cheaper. Plus you can make basic animations with the graphics. I don't know anything about animation or coding so I can't help you there.

Do you draw solely with mouse+keyboard? no use of brushes and paints?

To be fair I'm a novice at designing, but yes I do use mouse and keyboard. I don't use brushes or paints, and I don't download custom brushes (I see what I can do with stock tools). If you have a tablet they are great for helping you get into it but not essential to the point where you should buy one for the sole purpose of graphic designing (unless it was your only job or something).