First of all, I have two monitors.
I also use 2 monitors, and on the rare occasion I can't use 2 (like at school), I feel like my computer is crippled.
For me and the way I post, this is almost a requirement. Almost every time I post I do a lot of research, which means having my left monitor filled with a browser with 3 or 4 tabs open to reference sites, and the right (my main one) with the post I am replying to. And when things are slow, I can have anything else on the left side I want, full screen movies, or full screen maps for a difficult area I am working through on a game while it is open on the right side.
As for the title of this thread, I am going to take it literally, as computer tips, not browser tips.
Two screens, do it. After a week or so I can guarantee that you would wonder why you had never done it in the past.
ReadyBoost is another one. If you use any version of Windows from Vista on, this is built in. Basically you take a USB flash drive and turn it into a cache drive. This speeds up many operations, and effectively gives you a big boost in RAM for very little money (some version sof Linux have this also, like the DragonFly BSD with "swapcache").
Do not buy a desktop computer from the mass marketers (Dell, HP, Gateway, etc), but find a good reputable local computer builder. They use industry standard parts, are much easier to upgrade, are generally of a higher quality and just all around better. I built my computer in 2007, and it is still performing wonderfully. 1 CPU upgrade (dual core 3000 for dual core 6000), 2 video card upgrades, and a few other tweeks and my 6 year old computer still screams and has no problems playing even the newest games. How many 6 year old HP's or Dell's can make a claim like that?
And when you find a reputable computer place, bring your computer in annually and see what they recommend for upgrades. A good store qould suggest things you actually need, not just try and sell you things to make money. For example, if you bought your computer 3 years ago and it is getting slow, they might be able to just give you an upgraded processor and more RAM, and you would be good for many more years, at a fraction of the cost of a new computer.
Always keep your Antivirus current, I can't stress that one enough.
Run a good anti-spyware program also. I use several, but SpyBot is one of the best, and it is free.
Update your OS and protection programs regularly, at least weekly.
If you are one of those that leaves your computer running 24-7, give your computer a fresh reboot at least once a week.
Backup, backup, backup, backup, backup. I can't stress that one enough.
Add a second drive, and keep all your data (pictures, movies, music, documents, etc) on that drive. That way in case something happens and your computer does need to be reloaded, you do not have to worry about loosing anything important. It also increases the space available for programs on your main drive (I frequently have 3-6 hard drives in my computer).
Do not shop for a computer based purely on price. If we bought cars the way most people shop for computers, everybody would be driving around in Yugo's and Geo Metro's. Remember, you get what you pay for. Yes, I can build and sell brand new computers for $400, just like Dell does. But I will not, because I refuse to use parts and components of that poor of a quality.
I can go on for hours, but these are some of the most important ones I could think of.