Play Tag:

Once you build up a large list of bookmarks, keeping track of them all can get a little messy. To stay organized, you can assign tags to your bookmarked sites: just double-click on the star icon and you’ll be prompted to enter your tags.

You can tag a site with as many terms as you want (be sure to put a comma between each tag), and then easily find the sites again by typing that tag into the location bar. For example, entering "travel" into the location bar will bring up all the sites you’ve been bookmarking as part of your vacation research.

Learn All About Add-ons:

The standard version of Firefox is full of features, of course, but why stop there? There are more than 5,000 Add-ons — little extras that customize Firefox — that you can download to enhance almost any task you can think of. Go to Tools → Add-ons to open the Add-ons Manager and discover all the ways you can make Firefox your own.

Search Smarter:

You’re already familiar with the search bar built in to Firefox. But did you know you can customize it with just about any search engine you want? Just click on the icon to the left of your search bar to see the menu of default options.

Even better, click Manage Search Engines… to rearrange the list, add additional choices and even assign keyboard shortcuts to your favorite search engines. For example, you could give Google the shortcut "G" - then if you wanted to do a search for cookie recipes, simply typing "G cookie recipes" in the location bar would generate the full list.

Find it in a Flash:

The Find As You Type feature is another handy timesaver. Rather than using the “find” bar to search for a word on page, just hit the / key and start typing the word you want. Your cursor will immediately jump to the first instance of that term.

You can use it for links, too. For example, instead of moving your mouse across the page to a "learn more" link, just start typing the word and when the cursor finds it, press enter.

Eliminate Every Trace:

For security and privacy reasons, it's not good to leave a trail behind you as you browse (especially if you’re using a shared computer). Firefox lets you erase your browsing and download history, clear your cache and delete your cookies in a single click. Just go to Tools → Clear Recent History… to make it happen. Or, to be extra careful, go to Firefox → Preferences → Privacy and select the "Always clear my private data when I close Firefox" option.