Using a common ground is a good concept and works well for most electronic circuits. But often you don't want to have the ground return currents flow everywhere because heavy and spiky ground currents can erode the integrtity of common ground by introducing ground noise: They just produce voltage drops across the ohmic resistances and inductances of ground connections.

One way to control the ground return currents is to use the star point ground routing technique which was discussed here many times, e.g. here:

http://www.8052.com/forum/read/53375

http://www.8052.com/forum/read/94134

Today we tend to use solid ground planes to be able to comply with the CE standards and to make our circuits immune to ESD, surges, bursts, radiation etc. To control the ground return currents we arrange the circuitry on the board in such a way that the noisy ground return currents have short connections and don't flow over sensitive areas.

A bit provokingly spoken using a solid ground plane can be thought of as using a "very big" ground star point.

For a newbie using a printed circuit board with a solid ground plane and arranging the circuit moduls properly over the board by strictly separating the more sensitive parts from the less sensitive is the prefered way to go. And, as Per already mentioned, properly filtering can extremely help to control the ground returns currents in height and direction. But this heavily depends on your application. So, no further recommendations can be given here.

Kai Klaas