http://dl.google.com/android/installer_r15-windows.exe

a) Need to install the JDK, if you don't have it already.(http://java.sun.com/javase/downloads/index.jsp)

b) If you will be developing in Eclipse with the Android Development Tools (ADT) Plugin(http://www.eclipse.org/downloads/)

  The "Eclipse Classic" version is recommended. Otherwise, a Java or RCP version of Eclipse is recommended.

a) If you downloaded a .zip or .tgz package (instead of the SDK installer), unpack it to a safe location on your machine.
  By default, the SDK files are unpacked into a directory named android-sdk-<machine-platform>.

   b) If you downloaded the Windows installer (.exe file), run it now and it will check whether the proper Java SE Development
  Kit(JDK) is installed (installing it, if necessary), then install the SDK Tools into a default location (which you can modify).

   c) Make a note of the name and location of the SDK directory on your system—you will need to refer to the SDK directory later,
  when setting up the ADT plugin and when using the SDK tools from the command line.

a) Follow these steps to download the ADT plugin and install it in your Eclipse environment.

        i) Start Eclipse, then select Help > Install New Software....

        ii) Click Add, in the top-right corner.

        iii) In the Add Repository dialog that appears, enter "ADT Plugin" for the Name and the following URL for the Location:
        https://dl-ssl.google.com/android/eclipse/
        (If you have trouble acquiring the plugin, try using "http" in the Location URL, instead of "https" (https is preferred for security reasons).

        iv) In the Available Software dialog, select the checkbox next to Developer Tools and click Next.

        v) In the next window, you'll see a list of the tools to be downloaded. Click Next.

        vi) Read and accept the license agreements, then click Finish.

b) Configuring the ADT Plugin - the next step is to modify your ADT preferences in Eclipse to point to the Android SDK directory:

    i) Select Window > Preferences... to open the Preferences panel (Mac OS X: Eclipse > Preferences).

    ii) Select Android from the left panel.

    iii) For the SDK Location in the main panel, click Browse... and locate your downloaded SDK directory. Click Apply, then OK.

a) You can launch the Android SDK and AVD Manager in one of the following ways:

        i) From within Eclipse, select Window > Android SDK and AVD Manager.

        ii) On Windows, double-click the SDK Manager.exe file at the root of the Android SDK directory.

        iii) On Mac or Linux, open a terminal and navigate to the tools/ directory in the Android SDK, then execute: android

   b) To download components, use the graphical UI of the Android SDK and AVD Manager to browse the SDK repository and select new or
  updated components, The Android SDK and AVD Manager installs the selected components in your SDK environment