Using Firebug
Firebug is there when you need it, but doesn't get in your way when you don't. There are plenty of options for configuring how and when Firebug springs into action.
Use that second monitor
Free Firebug from the tiny confines of the browser and give it a whole window to play with. If you have two monitors, you'll work even faster with Firebug in one window and Firefox in the other.
To open Firebug in a separate window, customize the Firefox toolbars and add the Firebug button. You can click this button, or use Control+F12 (or Command+F12 on Mac) for fast keyboard access.
Blacklists and whitelists
Sometimes you just want to browse without thinking about code and errors. Firebug lets you keep a list of websites that it should or should not be enabled for.
You can browse in two modes - either enable Firebug for all websites except those on the "blacklist", or disable Firebug for all websites except those on the "whitelist".
F12 is your friend
The F12 key is undoubtedly the fastest way to get to Firebug. Train yourself to hit that key when it's time to go debugging. If you're the big screen type, use Control+F12 (or Command+F12 on Mac) to open Firebug in a separate window.
Put down your spectacles
If you find yourself squinting at Firebug, don't press your nose against the monitor, just make the font larger. Firebug lets you increase or decrease the size of its fonts to your heart's content.