For me several settings have to be done after a fresh installation of FireFox.
When searching, display the result in another tab: The value of
browser.search.openintab must be set to true.
For safety reasons, block referer headers: The value of
network.http.sendRefererHeader must be set to 0. (Link)
When you do not want websites to know where you are: The value of
geo.enabled must be set to false. (Link)
Install AddBlock. (Link)