Firefox Tips & Tricks

You can use Firefox in headless mode to generate screenshots. For example:
firefox --screenshot nightly.png
Try it and see.

Awesome Bar

Press Ctrl/Cmd + L which takes you to the Awesome/Address/URL Bar, then hit %, space and start typing and you will be searching your open tabs, use the up and down arrows and hit enter on the one you want and you will switch to it, very handy!

Then have a look at Awesome Bar - Search your Firefox bookmarks, history and tabs from the address bar | Firefox Help for some more handy options, other than %.