Hi All,
I have the following things in mind while routing a board:
-The return current of a track is under the track, therefore I always have a ground plane under everything.
-Loop antenna's are formed when the current can't flow under the track, so don't interrupt your ground plane.
-Dipole antenna's, or patch antenna's are formed when there are 2 separate ground planes. Always have one big ground plane, just to destroy the antenna. The return currents from noisy circuits will not propagate through, because they want to be local (under the forward track).
-When drawing noisy switching power supply's take 3 color pens, and draw out the current loops in your schematic. Then, on your board minimize the area those current loops make. This will prevent the current from flowing in a loop antenna.
-Place a ground plane under micro controllers, and interrupt it as little as possible. The closer the ground plane is to the chip, the more the fast currents in the chip are able to have a return path.
-via's are free, use them generously to stitch 2 ground planes together. If you have a track in the ground plane, make sure you have a ground plane at the top as well, and place via's so the return currents have a short path to keep following the forward currents in the tracks.
-Also use a lot of ground via's on an etched board, just drill holes, and then solder a wire on both ground planes. Not every via has to be made on the prototype, but they need to be present in the final product that's made by a board house.
-but most importantly: Think in currents, and antenna's.
Cheers,
Cedric