Create a shortcut. Right click it and go to properties. In the Target field, append -console to the end outside of the quotes.
"C:\Program Files (x86)\Activision\Vampire - Bloodlines\vampire.exe" -console
In the Library tab, right click the game and go to properties. Click set launch options… and add -console then click OK.
The console should be visible upon startup of the game. It can be hidden/shown by pressing the tilde or `/~ key. Sometimes the console can glitch a bit and can only be closed by pressing the tilde key, or by clicking the x in the top right corner. It can also freeze the game, but can usually be unfrozen by opening and closing the console again.
To issue a command, enable the console and type the basic format:
<command or variable> <value>
so for example..
cl_showpos 1 bind "MWHEELDOWN" "+jump"
A list of all commands can be found by typing cmd into the console.
|blood||get about 75% full blood pool|
|blood #||sets blood pool to given #|
|giftxp #||sets experience points to given #|
|mat_fullbright 1||makes level bright|
|money #||sets female breasts size to given #|
|noclip||disable clipping, walk through walls|
|notarget||invisible to all NPCs|
|quit/exit||exit to desktop|
|showtriggers 1||shows trigger boxes, must reload level|