Question: What are your tips for improving overall system performance on ubuntu? Inspired by this [question](https://askubuntu.com/q/2099) I realized that some default settings may be rather conservative on Ubuntu and that it's possible to tweak it with little or no risk if you wish to make it faster.

This is not meant to be application specific (e.g. make firefox load pages faster), but system wide.

Preferably 1 tip per answer, with enough detail for people to implement it.

A couple of mine would be:

* Install [Preload](http://techthrob.com/2009/03/02/drastically-speed-up-your-linux-system-with-preload/) (via Software Center or `sudo apt-get install preload`);
* Change [Swappiness](https://help.ubuntu.com/community/SwapFaq) value - "which controls the degree to which the kernel prefers to swap when it tries to free memory";

What are yours?

PS: Since this is not intended to have a unique answer but rather, several useful tips, I'm making this community wiki out-of-the-box.

Answer: 
If you edit video files, set up a stripped RAID 0 configuration for your video files. I noticed significant improvement in the smoothness of video editing after I did this.

<http://en.wikipedia.org/wiki/Standard_RAID_levels#RAID_0>

Of course you will need a minimum to two hard drives to do this, and it's easier if they are separate from the drive the OS is on (If you only have two hard drives, as I did, you can create a mirrored, RAID 1, boot partition and then a RAID 0 partition for everything else).

Note that since RAID 0 provides no fault tolerance or redundancy, the failure of one drive will cause the entire array to fail; as a result of having data striped across all disks, the failure will result in total data loss.
**ADVANCED, DO NOT DO IF YOU DO NOT KNOW WHAT YOU ARE DOING**

Compile your own kernel. <http://www.overclock.net/a/how-to-configure-and-compile-a-custom-linux-kernel-for-ubuntu> It may take quite some time, so do something else while you compile it. Once you're done, install the files and celebrate. Especially if you get huge speed improvements. :D