1. Use a lightweight window manager

KDE and GNOME aren’t just window managers, they’re “desktop environments.” For years, KDE and GNOME have competed to provide the most featureful graphical user interface for Linux. And with all those features comes a lot of CPU and RAM usage. Historically, this has meant that either of them worked really well on the lastest processors with plenty of RAM, but not so well on older systems. In modern terms, with modern versions of the software, KDE and GNOME’s slowness is likely imperceptible on a dual-core machine with at least 1GB of RAM, but is likely noticable on anything older or less-well-powered than that.

Me, I use a tiling window manager named w3m. It sacrifices a large number of bells and whistles in order to occupy a very small footprint. This is pretty much at the bottom of the weight scale, as far as window managers go, though there are a few that are more-lightweight, and it’s possible to do without a window manager entirely, in some situations.

If you don’t want to learn something radically different from GNOME or KDE, try XFCE or Enlightenment. If you’re feeling a little more adventurous, try Afterstep or WindowMaker.

One of the things you’ll discover if you switch down from GNOME or KDE, however, is that most of the other window managers won’t automatically mount CDs, flash drives or floppy disks for you. You can still do it manually, and it’s possible to set it up to occur regardless of your window manager, but it’s something you’ll likely have to deal with.

2. De-select the unnecessary services
On any modern operating system, there are tens of programs running in the background, handling things without direct interaction from you. Most of these programs are started while you’re booting up, at various “init” levels. Disabling these services means that your computer won’t have to start them while you’re still booting up.

I can’t tell you what’s safe to disable in your case, but I can tell you to be careful. Each program is there because either the maintainers of your distro thought it would be a good idea for it to be there, or because your system administrator thought it would be a good idea for it to be there. Removing them can cause issues ranging from a slow system (Such as when I disabled PulseAudio on my laptop a while back, and had to wait for programs using ALSA to timeout.) to a severely broken system. Killing inetd may make your system inaccessible from other computers. Killing ntpd could make your clock start running fast or slow. Killing klogd and syslogd could cause all sorts of problems.

3. Use a text-based login in lieu of Graphical login window

Technically, it’s called a “display manager”, for those interested in the terminology.

This is certainly a possibility, but it has its own drawbacks. While you can avoid having to start gdm, kdm or xdm (which do take a significant amount of time in my system’s boot cycle…and I’ve got a top-of-the-line home-built desktop.), you’ll have to learn at least a little bit about the command-line interface of Linux. Which is something you should do in any case if you plan to be proficient in using and administering your Linux box, but it’s something you should be ready for, rather than surprised by.

Additionally, some modern distros coughubuntucough write a lot of messages to virtual-terminal console screens. These are the types of screens you’ll be seeing initially if you get rid of gdm, kdm and xdm. As a result, using virtual terminals for system operation can get frustrating, as these message will often overwrite or push out whatever it was you were trying to see.

By the way: the “startx” command is the one you’ll most likely be looking for first if you remove gdm, xdm and kdm.

4. Use a lightweight Linux distro
In my experience, light-weight Linux distributions that aren’t targeted to specific system purposes are essentially the same as the heavier distributions, but with some of the above steps already taken care of. They’ll often use XFCE instead of GNOME or KDE, for example, and they’ll use lightweight alternatives to OpenOffice, rather than OpenOffice itself. Sometimes they’ll replace Firefox with Galeon or Opera.

All in all, they’re good choices if they will do what you need them to do. However, keep in mind that it’s the popular distributions that have the most community support. If you need assistance with something, you’ll probably find help easier if you use Ubuntu or one of its derivatives than if you use Fluxbox.

5. Disable unnecessary kernel modules - Only for Geeks and Administrators!
If you’ve used wifi on Linux, there’s a good chance you’ve already skirted this one. Otherwise, be very, very careful. Messing around with your kernel configuration is Risky Business, and not something to be done unless you can put up with making mistakes a couple times in the process. And these mistakes can mean everything from making the system unbootable to corrupting the data on your hard drive.

(That said, it was one of the first things I did when I first tried Linux as a kid. But I made lots of mistakes at first and lost my data a number of times. My friends–the ones who’d gotten me into Linux in the first place, and who were package and software maintainers on their own time–had no help to offer, as they hadn’t messed with it themselves.)

Hope that helps.

I never boot up my computer, just press the space bar and 2 seconds later I log in.

Greetz Erik