Really cheap way to get infinite experience (spoiler!)

[Master_Deeje]

When on korriban and you have already been accepted into the sith academy talk to yuthura ban and ask her about the sith code. Afther she's done explaining and asks you what part do you not understand simply say "I think I got it" and after you have ceased speaking with her for each time you asked her about the code you will recieve 125 XP

[Jack Dell]

also on korriban but much faster and with a much larger payload of xp, use TM (utility droid) who should have an insane computer use skill, and countinuosly hack the duel arena computer (the one in the sith academy that spits out prisoners) for 0 spikes cost, and each time you do it and exit, it will give you lots of xp, and also unlike other xp bugs, this one does not require you to cycle through long dialogues with npcs. So if youre looking to try out new classes but dont want to wait to the end of the game to see them in full bloom, just go to korriban first and do this and you should reach 20 in a relatively very short time. I did not use it because I must play legit, but its still there. Also, if Im not mistaken, it does not have a penalty as you increase level, whereas if you train with respaning monsters (like the wraids) you receive a penalty of xp amount the higher the lvl, essentially making it terribly slow to lvl up beyond higher levels.