When your main character, the exile, becomes level 15, you can talk to Kreia to become a Prestige Class. Which Prestige classes you can choose from, depends on your alignment. If your bar is on the Light Side. You can get Jedi Watchmen, the stronger Jedi Sentinel, Jedi Master, the stronger Jedi Consular, but you'd be better off with a Consular, because of the Defence is higher on the Consular. And then there's Jedi Weaponsmaster, the stronger Jedi Guardian.

For people whose bar is on the Dark Side, you'll get Sith Lord, like the Consular, only Defence is ok and better, Sith Assasin, like the Sentinel. And last but not least, Sith Maurader, like a Guardian.

Decide what you want!

NOTES:You will get a level up after you get your prestige class. And when you come to Dark or Light side Mastery, you get diffrent bonuses depending on your class. Example. You get 50+ FP For choosing Sith Lord and then getting Dark Side mastery.