Linux Howtos
These howto(s) try to be the generic way of getting things configured. They work on a recent Slackware-distribution but should do as well on any other recent distribution.
Audio
Multiple Sounddevices
Assuming you have a soundcard and an usb-Headset which may or may not plugged in at boottime. The order of sounddevices will not be consistent because, if plugged in at boottime, the usb-device is loaded at first by the hotplug-mechanism.
Solution: Manually set the default order of the sounddevices.
As "root"-user, look what devices are avilable.
cat /proc/asound/cards
0 [Headset ]: USB-Audio - Logitech USB Headset
Logitech Logitech USB Headset at usb-0000:00:1d.7-3.3, full speed
1 [Intel ]: HDA-Intel - HDA Intel
HDA Intel at 0xfea78000 irq 43
Check if the corresponding modules have been loaded by the kernel.
lsmod | grep ^snd_hda_intel
lsmod | grep ^snd_usb_audio
Make the order(Intel as default device) consistent, regardless whenever the headset is plugged in.
/etc/modprobe.d/sound.conf options snd slots=snd-hda-intel,snd-usb-audio
Reboot.
More infos in the Kernel-Documentation:
/usr/src/linux/Documentation/sound/alsa/ALSA-Configuration.txt