From WeatherCat Wiki
The following are resources that may be helpful when attempting to locate your weather instruments for best accuracy and performance.
- CWOP Weather Station Siting, Performance, and Data Quality Guide 
- Personal Weather Station - Siting (NOAA)  Includes URL's to other interesting documentation.
- Royal Meteorological Society - A Guide to the Siting, Exposure and Calibration of Automatic Weather Stations for Synoptic and Climatological Observations (Andrew K. Overton)