After completing each level, do not continue. Instead, leave the diner and break all "trash cans" by the doors outside. You can sometimes get a few thousand studs. Additionally, in the Discovery On Kamino level, if you encounter the broom where you had R4 to open the gate, use the Force on it. Money will come out. If you follow it around the entire room, money will still appear. This is useful when trying to get perfect studs.