Robert Taylor from TI highlights some pointers when thinking through your power supply layouts, for EE Times:
Power supply layout is a very tricky subject. The first step is to identify how the currents flow in the power supply, then find and minimize the high-frequency loops. Next use both ground and power planes to connect components in a very low impedance manner. Make sure the planes used are wide enough to carry the design current. Make high-frequency switching nodes as small as possible to reduce any chance of noise coupled to other signals. It is also good practice to use a large continuous ground plane with many vias to connect grounds of different components. If you follow this list of tips and rules, you should be successful at designing your next power supply.