How do I access the console?

To enable the console create a shortcut that appends +seta com_allowConsole “1″ to Quake 4 and press ‘ (UK key below ESC) or CTRL+ ALT+ ~ (US Keyboards) or CTRL+ALT+ ‘ (UK Keyboards)

Quake4.exe +seta com_allowConsole “1″

or use the following to skip intro animations / movies and enable the console

Quake4.exe +seta com_allowConsole “1″ +disconnect

How do I alter my default FOV?

Use the console command g_fov to alter your fov in singleplayer and multiplayer. In patch 1.1 or above maximum player is no longer limited to 110.

Example:

seta g_fov 110

How do I record and playback demos?

Use the console commands recordnetdemo demo_name, recorddemo demo_name,  playnetdemo  demo_name, playdemo  demo_name and
playdemo stop. Example:

Multiplayer (Smaller Demo Files)
recordnetdemo uc_vs_uc // starts demo recording
stopnetdemo // stops demo recording

playnetdemo uc_vs_uc // starts demo playing
stopnetdemo stop // stops demo playing

Singleplayer
recorddemo UCLevel1Tips // starts demo recording
stoprecording // stops demo recording

You can also save hard disk space while recording demos by setting com_compressDemos to 0, 1, 2, or 3.

0 – No compression, creates large demo files
1 – Fast compression and decompression, creates small/medium demo files
2 – Slow compression and fast decompression, creates small demo files
3 – Fast compression and slow decompression, creates medium size demo files

You can also use the command compressdemo to compress a demo
Can I setup Quake4 for Widescreen?

Quake4 ships with Widescreen options in the Settings menu. You can also  setup custom resolutions using the cvars r_customHeight, r_customWidth, r_mode and custom aspect ratios using r_aspectRatio. In patches from version 1.05 r_aspectRatio can be set for 4:3 (seta r_aspectRatio “0″), 16:9 (seta r_aspectRatio “1″) and 16:10 (seta r_aspectRatio “2″)

Example for 16:9 PAL (UK etc):

seta r_customHeight “576″
seta r_customWidth “720″
seta r_mode “-1″
seta r_aspectRatio “1″

Example for 16:9 NTSC (USA etc):

seta r_customHeight “486″
seta r_customWidth “720″
seta r_mode “-1″
seta r_aspectRatio “1″

Add the custom resolution settings to a text file called autoexec.cfg in your Quake4 ‘Base’ directory.

How do I customise my crosshair?

You can customise your crosshairs using the cvars g_crosshairCustom, g_crosshairColor, g_crosshairSize and g_crosshairCustomFile.

g_crosshairCustom specifies if you want to use custom crosshairs
g_crosshairColor is used to set the crosshair colour ( R G B Alpha)
g_crosshairCustomFile stores the custom crosshair’s filename
g_crosshairSize sets the crosshair size which must be 16,24,32,40,48

…more to follow

Source: UpsetChaps