For me it's all about the lightsaber:
1) Nar Shadda: Mostly because you get the lightsaber the fastest here.
2) Right after you get your lightsaber take a quick jog to Dantoine to pick up the "your name" crystal
3) I go back to Nar Shadda from here just because I like Mira/Hanharr best in the game so I like to get them asap.
4) Back to Dantooine. I hate unfinished business.
5) Onderon. The robes and stuff there are just way too cool.
6) Koribann