NOTE: I would advise placing all your installation under ONE FOLDER in a path without spaces(must be followed), e.g C:/AndroidInstallers. For your workspace, might as well place under drive C with folder name AndroidWorkspace.
1. Download and install both JDK and JRE from here: http://www.oracle.com/technetwork/java/javase/downloads/index.html
2.Download and install SDK from this site: http://developer.android.com/sdk/index.html
3.Download and install Eclipse for windows user from http://www.eclipse.org/downloads/
4. You may follow instructions in installing Android in Eclipse from either of the following sites:
4.a. From the “Downloading the ADT Plugin” section of http://developer.android.com/sdk/eclipse-adt.html
5. Makes sure you have made AVD/Emulator using the SDK and AVD Manager. Consider making AVD’s for all versions available.
6. Do instruction under “Configuring the ADT Plugin” section in http://developer.android.com/sdk/eclipse-adt.html
7. You may now make a sample program like “HelloWorld” following the instructions from http://developer.android.com/resources/tutorials/hello-world.html.