Better Default Google Search
One of Firefox's coolest features (though it's hardly undocumented) is its ability to search from the address bar. When you enter a search term in the address bar, the browser redirects to Google and searches that term automatically.
But these results are of Google's "I'm Feeling Lucky" persuasion: You're sent to the most popular page that matches your criteria. Only if there's no clear winner will the search engine list everything it finds.
If you'd rather not trust to Google's luck, change this setting by editing Firefox's configuration file. This is one important file, so back up it first--see "Back Up Firefox's 'Registry'" below for details.
With your backup in place, type about:config in Firefox's address bar and press Enter. In the resulting page's Filter field, enter keyword (you won't have to press Enter this time).
Double-click the keyword.URL entry (as illustrated in the first of the two screens here, the one at left); then enter, as a single line with no letter spaces, the entire string shown below:
Click OK. Now when you enter a search term in the address bar, you'll get a full page of Google search results, just as you would if you'd entered the keyword on Google's home page.
If you decide later that you should've trusted Google (a familiar refrain in Silicon Valley), you can reverse your fortunes by repeating the steps, but this time enter this string (again, as a single unbroken line):
Back Up Firefox's 'Registry'
Firefox's about:config screen is like Windows' Registry--it contains important information, but is obtuse and dangerous to fiddle with. So play it safe by backing up the configuration file before you make any changes. To do so, close Firefox, select Start, Run (just Start in Vista), type %appdata%\mozilla\firefox\profiles, and press Enter. The resulting Windows Explorer window will contain a folder with a very strange name, like '4hw0enat.default' (as illustrated in the full screen of the thumbnail at left). Open that folder, and then copy the file prefs.js to a safe location.
Better yet, make sure that the Profiles folder is included in your regular, daily backup routine. Should you mess something up in about:config, simply close Firefox and copy the backup of prefs.js back to its original location.
Add to the Search Bar
You can add, remove, and organize the services listed on the Search Bar in the Firefox window's upper-right corner.
To do so, click the area to the left of the search box and select Manage Search Engines from the drop-down menu that appears. In the Manage Search Engine List dialog box, click Get more search engines to view a list of available search services.
To add one, simply select it and click Add. If you want Firefox to use that service as its default search engine, check Start using it right away, and then click Add.
Since you can search through Google via the address bar, you might want to remove Google from this list. To do so, select its entry and click Remove.