Find the file called "swkotor2.ini" in your Knights of the Old Republic game folder. Edit the file with Notepad and under the line [Game Options] add the following line:
EnableCheats=1

While playing, press ` (below tilde) and [ENTER] or [SPACE] to activate the console then type any of the following cheat codes followed by [ENTER] (may need to use ENTER on the num pad):

Note: The following file (kotor2cht.zip) contains a modified version of the kotor2.ini file with the EnableCheats line added. You can replace your kotor2.ini file with this one if you are having trouble modifying the file. Always make a backup before overwriting configuration files. You may lose all or part of your configuration for the game if you use this file instead of modifying your own.

Editor's Note: It's been stated that you cannot see what you're typing when entering the cheats. Some have reported that they are not working, and this turned out to be the case. If the console is activated, you will know as your character will stop moving. Whether or not you can see the console, follow the instructions and the cheats will work fine.

Code - Result:

heal - Heal Player
addlevel - Add Level Experience
whereami - Show Location on Map
infiniteuses - All Limited Use Items are Infinite
revealmap - Reveal Map (using M key)
givecredits XX - Give XX # of Credits
giveitem - Give Item of Your Choice
givemed - Give 100 Med Kits
giverepair - Give 100 Advance Repair Kits
givecomspikes - Give 100 Computer Spikes
givesecspikes - Give 100 Section Spikes
givesitharmour - Give 100 Armor
setcomputeruse XX - Set Computer Skill Level to XX
setdemolitions XX - Set Demolitions Skill Level to XX
setstealth XX - Set Stealth Skill Level to XX
setawareness XX - Set Awareness Skill Level to XX
setpursuade XX - Set Persuade Skill Level to XX
setrepair XX - Set Repair Skill Level to XX
setsecurity XX - Set Security Skill Level to XX
settreatinjury XX - Set Treat Injury Skill Level to XX
setstrength XX - Set Strength Skill Level to XX
setdexterity XX - Set Dexterity Skill Level to XX
setconstitution XX - Set Constitution Skill Level to XX
setintelligence XX - Set Intelligence Skill Level to XX
setwisdom XX - Set Wisdom Skill Level to XX
setcharisma XX - Set Charisma Skill Level to XX
addexp XX - Add XX to Experience
turbo - Characters Move Faster
invulnerability - God Mode
restartminigame - Restart Mini Game if You Lose
bright - Turn Dark to Bright
addlightside XX - Add XX to Light Side Experience
adddarkside XX - Add XX to Dark Side Experience