This post will consist of mainly links to guides which I used in setting up my development environment to write Android apps.
Step 1. Install Eclipse as per usual http://www.eclipse.org/downloads/ (I always install the Classic package, but I’m not sure if that is the best way to go)
Step 2. Download the Android SDK http://developer.android.com/sdk/1.5_r2/index.html (I don’t think it matters where you unzip it to, as long as you can find it later)
Step 3. Follow set up instructions http://developer.android.com/sdk/1.5_r2/installing.html
Step 4. Learn about how to create and run Android projects http://developer.android.com/
A few gotchas:
Android has a built in JSON feature which is explained here: http://developer.android.com/reference/org/json/JSONObject.html
Java does not ordinarily have JSON packages included (as far as I know), and if you include json_simple or similar packages, Eclipse will no longer recognize the Android JSON package.
This happened to me, and I had trouble figuring out how to tell Eclipse to ignore the package I no longer wanted. An easy work-around is to remake your project and copy/paste source files.