Make a shortcut to your desktop of "daorigins.exe" (Dragon Age/bin_ship/daorigins.exe) go to shortcut properties, and under Target add -enabledeveloperconsole (after ..daorigins.exe" )

This can be done on the Steam version by right clicking on the game in your Games List, choosing Properties, and clicking Set Launch Options. This allows you to enter command line option.
Then go into the keybindings.ini file located in "My Documents\BioWare\Dragon Age\Settings\" Find the line "OpenConsole_0=Keyboard::Button_X" (GRAVE is default, change X to any button that is not already used in the game.)

Save the file, and start the game with the shortcut you created on your desktop (daorigins.exe - shortcut)
In-game, you press the key that you have chosen (Keyboard::Button_X) and then type the following codes: (Note, this has only been tested on the retail version, and not the Steam version. Also, you may not see the console, or what you are typing, this is normal.)