The instructions on the Google site for setting up for Android development within Eclipse on Windows is pretty good. However, there are a few things to watch out for (as of today, July 23, 2010):

• Stay away from Eclipse 3.6. The Android Plug-in does not fully support it.
• Choose the 64 bit Windows version of Eclipse 3.5 (SR2) classic.
• Choose the 64 bit version of the JDK 1.6 update 20. There are reported problems with update 21 and Eclipse.