Instructions
Choose the evil and malicious side whenever you get a choice. Early in the game, for example, you have the chance to help a girl who has a price on her head. Kill her instead and collect the reward.
Exploit and backstab characters whenever you can. When someone asks you for help, do it for pay instead of for good. If you have the choice of killing them afterwards, do it.
Hang around the Dark members of your party during the game. Half your party members are light and half are dark, and each has his own story. Knowing the Dark Side members will further your quest to their side.
Fight as many people as you can. Whenever the choice comes, always take action over talk. Picking fights with innocent non-player characters always scores points toward the Dark Side.
Kill off other team members if you have the choice. Jolee and Juhani are two characters you can kill during the game, and you'll have multiple chances to do so.
Destroy the Sith Lord Malak for your own purposes at the end. If you agree to help the Jedi defeat the Sith, you may still be saved for the good side. Instead, kill him with the purpose of surpassing him.