/diy/ - Do It Yourself

I am using the LTC1707 buck regulator to step down from ~6V (4 aa alkaline cells) to 5V. I am confused about proper grounding. Initially I used a common ground and this caused Vout to be 6V when Vin was 6V so I knew I did something wrong. Then I re-read the datasheet PC board layout checklist where it mentioned segregating signal and power grounds. I probed Vout and R4 and sure enough it showed 5V. I did this on a breadboard but now I'm going to solder it more permanently. Should I be using this point on the resistive divider (R4 lead) to ground the rest of the circuit that will be using the 5V Vout? Also I'm unsure about the star ground formation. I gather it's when a single point connects the ground planes. So Since R3 is connected to power ground does this complete the star ground formation?