Press ~ and type "DebugMode 1", then press ~, press Tab to view the debug commands. Press Tab again to scroll through the commands. Now you can enter one of the following case-sensitive codes:
Invincibility: dm_god
Restore all hit points: dm_heal
Get all spells: dm_allspells 1
Get indicated spell: givespell [number]
Get indicated amount of experience points: GiveXP [number]
Get indicated amount of gold: dm_givegold [number]
Spawn indicated item: giveitem [item code]
Set character level: dm_givelevel [number]
Raise indicated number of levels: GetLevel [number]
Set Strength attribute: SetSTR [number]
Set Dexterity attribute: SetDEX [number]
Set Intelligence attribute: SetINT [number]
Set Wisdom attribute: SetWIS [number]
Set Constitution attribute: SetCON [number]
Set Charisma attribute: SetCHA [number]
Set character's age: SetAge [number]
Set character's base attack: SetAttackBase [number]