If you've never done a wireless site survey before, get someone to do it for you and observe what he does.
You can't learn how to do wireless site survey just by reading books. You need to see how it's done. Ask relevant questions.
Tool wise -- AirMagnet Survey and AirMagnet Spectrum XT.
Site Survey -- I think it would be best to hire a respected contractor and tag along.
You can use the Ekahau Site Survey for an active site survey that is onsite to get the live readings, or if its predictive that is done with a floorplan. Usually active surveys are the best to go when designing for least RF, coverage, & location factor. Also below recommended software is good too.
Try use this tool ,its tested and give you the most accurate and precise decision in planning.
Hope this help and share your result also.
Below is the link for Site Survey Guidelines, Please let me know If the link is helpful