Herewith, the few (Windows) Firefox tricks that I find particularly handy, and a small rant.
You know how IE could be set to make each new window load whatever you'd been looking at in the last one? To make Firefox do the same thing with a new tab, make your new blank tab with ctrl-T, then press ctrl-Z to paste the contents of the last tab's address bar into the new tab's.
Troubled by drop-down autocompletion menus (for login names, for instance) that contain useless relics of past mis-typing...
...or evidence that you've been doing lots of searches for things that would make the rest of the National Association of Evangelicals very angry with you?
Cursor-down to any entries you don't want, and press shift-Delete. Bing, gone.
Also, you can cycle through tabs with ctrl-Tab and ctrl-shift-Tab, and close tabs without bothering to select them first by middle-clicking them on the tab bar (and, of course, ctrl-W closes the current tab).
That last trick isn't actually especially tricky, but it lets you do everything that the new Firefox 2 tab close boxes do, while leaving the close boxes turned off so you've got more room for actual tab text. You can also make the tabs work pretty much exactly as they did in Firefox 1.5, if you don't like the new horizontal scrolling and List All Tabs button - that's mentioned near the top of this Lifehacker piece.
The comments on that piece point out that the new "prefetch" feature is (a) not actually new, and (b) not as brillant as you might at first think. No, Firefox 2 (or various versions of 1, or Google Web Accelerator...) does not dumbly preload whatever the first link on the current page points to, or some such goofy thing.
Right now, I bet prefetch actually still doesn't do much at all. I suppose some sites must use the <link rel="prefetch"... syntax needed to make it happen, but it's not exactly rife. If prefetch ever does become really popular, though, it could indeed be a definite pain for dial-up users. Just because the browser's idle doesn't mean nothing else needs bandwidth, after all.
Oh, and people in offices with strict browsing policies could be in for all kinds of fun if some random page decides to invisibly prefetch a few porn and shock images, just for fun. Not that you can't do that already in several ways, but prefetch is the most 11-year-old-h4XX0r-friendly way to plant filth in someone's cache folder that I've yet seen.
