current approach:

As of now (Dec. 2009) most people will run a 2.6 kernel that does not necessarily be patched anymore.

A minimal way to achieve results in tuning a linux system for audio might be done by setting appropriate limits for your audio group in /etc/security/limits.conf:

@audio - rtprio 80
@audio - memlock 250000
@audio - nice -10

Further interesting lowlatency-related topics that include hints on kernel compilation can be found in the alsa wiki.

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• This section below mostly applies to the 2.4 kernel series and was last updated 2006.

heavily recommended:
The lck patch already includes the low latency and preemptible patches as well as other interesting stuff (i.e. variable HZ + 64bit jiffies).

The capabilities patch enables your system to run some parts with elevated privileges without compromising security. (Better than running everything as root)

FAQ
ftp site (down? old ?)
FIXME: no urls found.
well, it will also run without it...

Planet CCRMA has more info on linux kernel tweaks.

Gentoo has an overlay called proaudio here using Ingo Molnars real-time Kernel patches