Browse local copies of websites when possible (Firefox with slow internet connection)

Besides, the obvious, which is to make your cache ridiculously large (1GB here) there are a couple of settings you can set.

goto about:config

1. network.dnsCacheEntries: Increase number of DNS entries cached to something like 500.
2. network.dnsCacheExpiration: Increase the number of seconds to keep DNS cache.
3. browser.cache.disk_cache_ssl: Change to true to cache secure website. If you are like me, I use a completely stripped down browser for shopping and banking. Who knows what those addons are tracking. . .
4. network.prefetch-next: this one is debatable. I think it is off by default (false). Basically, a website usually specifies the next page and tags it. Firefox will search for that link and download it using idle bandwidth. Depending on your surfin habits, it may or may not be useful. I typically open a whole bunch of tabs (30 or so) at a time and then read them one by one. If I find the site useful, I'll keep surfing, otherwise I close it. This way, the browser downloads the next link while I read.
5. browser.safebrowsing.enabled and browser.safebrowsing.malware.enabled: Every 30 minutes, firefox will download a list of sites that are reported to be phishing or malware sites. Again, if you are like me, you use a separate, vanilla browser for banking and shopping. Plus, I have no need for these lists.

I'd also heavily consider the following addons: NoScript, Adblocker, SessionSaver.

• NoScript is a no brainer. If anything, just block Flash/Silverlight, video/audio. The other ones overlap with Adblocker. And apply it to Trusted sites and turn off "Ask for confirmation before unblocking an object". Also make sure to uncheck the options "Autotomatically reload pages when permissions change". Then you can just click the icon and click "Allow all on this page" when you get around to finally reading a tab.

Session Saver has a cool option where it turns off reloading of tabs upon loading a session. That way the tabs are only loaded up upon actually navigating to them, rather than all at once. Or you can tell it to load only a set number of tabs concurrently when you load a session.

Adblocker is a no brainer. Use it liberally to block banners, images and crap. There is a setting to block everything from a domain address only if you are at this explicit page you are on. That way you aren't blocking images from sites when you are actually at said address.

I hope these help. I feel your pain. My cousins are on AT&T and the highest that DSL goes in their area is 6Mbps. When you have the mother streaming netflix, the other two kids watching videos on their own laptops while the grandmother is trying to skype back to Germany. I told them they should just cough up for another DSL connection.

Thankfully, last week they got a good deal for cable internet. Like 20 bucks more for 12Mbps.

You could install a local web proxy cache on your computer. I guess that the configuration of a web proxy cache si much more flexible than firefox. Check squid.