How can I find a persons location by cell phone number
By calling their number and asking them where they are.
You can find their general location by the area code.
There are quite a few smart phone apps that can do that provided that the third party is signed up with them.
With the help of http://goo.gl/CxOQCV you can easily find someone's exact location using a phone number.
Using http://goo.gl/dJ8PRF can help you to locate someone with his/her phone number.