Firefox: Changing your search engine
Although several browsers let you change the search engine via a pop-up menu in their search bar, they go back to the default search engine the next time you open the browser. Thus, you need to change the search engine permanently in a Preferences or Settings window. But if you change the search engine in Firefox's search bar pop-up menu, it stays changed even after you quit and relaunch the browser. Now that's easy! (Note that Bing is not an option.) As shown here, you can add search engines by choosing the Manage Search Engines option.