This cheat sheet, put together by blogger Leslie Franke, will likely show you a couple new shortcuts or tricks with Firefox that you didn’t know of before. It includes a ton of useful information, including navigational shortcuts, tricks, hidden pages, search shortcuts (shown in image below) and much more.
 

If you are unfamiliar with Firefox shortcuts, I suggest you find some way to keep it nearby as you attempt to learn new shortcuts. These little tricks can save you a lot of time and increase your productivity as you browse the web. This sheet is sure to assist you to remember these shortcuts.

Just like any good cheat sheet, this one is clear, concise and to the point.  If you don’t feel like or don’t have the time to memorize all of the tips, just print it out and keep it by your side.  With enough usage you’ll memorize them anyway.  You can download it in a handy PDF file here.

Personally, I really enjoyed the search keyboard shortcuts part. Before seeing this document I always used Ctrl + F, but now I am warming up to /, and even some of the other methods

 
Firefox Cheat Sheet

PDF Version