After meeting with Vrook (ugh) and completing Dantooine, I head back to Onderon and finish the civil war there. Once civil war breaks out in Iziz, however, I head over to Dantooine. So, I like to start the first part fairly early in the story. Next, I head to Onderon (really, Dxun), because this planet has to be accomplished in two parts.
Furthermore, your conversation with the actual Goto aboard his yacht adds a level of urgency to the plot. (Spoilers) I like to go to Nar Shaddaa first, because you pick up a significant number of new companions there (Mira, G0-T0, and I believe you can finish finding all the parts for HK there).
