For many years now, I've used a low-impedance power and ground plane (It's not as easy now, with multiple power supplies required in nearly every circuit.), essentially a "pour" on the outer layers of the PCB. Major "swamping" cap's are placed in strategic locations, and small, typically 1nF cap's near each device. This generally, in a single-supply environment, keeps power-gnd noise in the 50 mV range.

Many vendors have recommended the use of ferrites to block high-energy noise from getting from one supply to the other, and to keep it localized. While this may, in most cases, improve things, I've had no results to support that notion. This doesn't stop me from using them, however.

RE