We started by going straight back to where the Emperial base was set up, and it was empty. Most people had begun to line up to meet Peter Mayhew (Chewbacca) and we got great pictures with Darth Vader and Darth Sideous without any wait. We also found that later after the Stars and Motor Cars parade that there was only a small line to get Peter Mayhew's autograph, and the same for the scheduled time for Rob Coleman (Visual Effects Supervisor for ILM) We seemed to plan our encounters pretty well for having no plans at all.
I do suggest continuing to tour the Emperial and Rebel Bases, if only for the additional characters that seem to come out during the day. By the afternoon, Greedo, Darth Maul, and Zam Wessel, among others, had joined the Emperial Base, and Queen Amidala and Anakin joined the Rebel Base...although they were seperated a little... (On a cute sidenote, the little girl in front of me, probably about 4 or 5, walked up to get her picture taken with Amidala, and Amidala leaned down and asked the girl if she had seen Anakin. The little girl shook her head and said not yet, and Amidala told her that when she did see Anakin, to tell him that she missed him....thought it was sweet...)