Tweaking Firefox for Performance

The biggest slowdowns are rarely come from ram usage these days. The best suggestions I think of right now are as follows.

1. Get a Flash blocker. Either Noscript or Flashblock. Personally I like no script better. It keeps flash videos from autoloading and autoplaying. Nothing kills performance like flash videos.
2. I'd also get a password/form fill manager, like LastPass. It's so satisfying to see a form with tons of fields and with two click, it will autofill everything with your information. Cake.
3. If you haven't already done so, up the cache size, From what I hear in the Mozilla support forums, 500 MB is a good size. Any bigger and you are wasting time just managing what's in the cache and purging it.
4. As an aside, a clipboard ring is handy, like Clipcube. Often times I'll run into multiple links I want to open up, but I don't want to run up more than 30 or so tabs. I can copy each one and Clipcube keeps them in a list I can bring up and paste them into firefox at my own pace.

Lastly, while there are other tweaks out there, I'm hesitant to really recommend any. A big part of performance is reliability. All it takes is one crash or one website not to load up completely and that kills all the time you've saved cumulatively.

The following is ripped from Up-to-date Tips: Increasing Firefox Performance (though I've fixed some typos and improved formatting) which don't seem that up-to-date but it might be helpful for you:

How to speed up the rendering of a page?

Add the following preference, Firefox will render the page immediately:

• Ctrl+L to go to the URL entry
• Type about:config to open the configuration editor
• Right click -> New -> Integer
• Type nglayout.initialpaint.delay as the preference name
• Type 0 as the value