1. Download the native client SDK and Python if you need it.
https://developers.google.com/native-client/sdk/download
Get pepper_canary, not the recommended versions.
D:\nacl_sdk>naclsdk update pepper_canary

2. Download chromium
2A. First, get the source tarball as described in "Bootstrap using the tarball"
http://dev.chromium.org/developers/how-tos/get-the-code
2B. Download the depot_tools
http://dev.chromium.org/developers/how-tos/install-depot-tools
2C. After downloading the gclient / depot tools, be sure to start a new command prompt so the addition to your PATH takes effect.
Exectute the section on "Check out the sources"

3. Copy the private headers from the chromium repo into the SDK repo
mkdir D:\nacl_sdk\pepper_canary\include\ppapi\c\private
mkdir D:\nacl_sdk\pepper_canary\include\ppapi\cpp\private
copy D:\chromiumtrunk\src\ppapi\c\private\*.h D:\nacl_sdk\pepper_canary\include\ppapi\c\private
copy D:\chromiumtrunk\src\ppapi\cpp\private\*.h D:\nacl_sdk\pepper_canary\include\ppapi\cpp\private

4) Enable the experimental UDP apis in Chrome
go to about:flags and enable "NaCl Socket API"

5. Install the visual studio update
http://mainroach.blogspot.com/2012/10/official-nacl-vs2010-add-in-available.html
D:\nacl_sdk>naclsdk install vs_addin
D:\nacl_sdk>cd vs_addin
D:\nacl_sdk\vs_addin>install.bat

Set the enviroment variable NACL_SDK_ROOT to D:\nacl_sdk\pepper_canary
Then see https://developers.google.com/native-client/dev/devguide/devcycle/vs-addin#add-platforms

6. Build as in make.bat

7. Run httpd.py

8. Press F5 to debug. There are these instructions, but I don't believe they are relevant:http://www.chromium.org/nativeclient/how-tos/debugging-documentation/debugging-with-debug-stub-recommended/debugging-nacl-apps-in-visual-studio-with-wingdb-using-debug-stub-experimental