Place a guard trace around each and every clock trace if the board is single or double sided (no ground plane present). Make the distance spacing as close as possible. With minimal distance between the signal and guard trace, and otherwise obey the 3-W rule. This minimizes crosstalk and provides a return path for RF current.
For high-threat signals, use of a shunt trace provides additional RF suppression by providing an additional ground return path for common-mode currents that may exist on a trace in a board with dual stripline topology.
When using guard and shunt traces, make connections to the ground planes at irregular intervals throughout the route. Symmetrical grounding allows for a tuned circuit to be created that may be resonant at a particular harmonic or wavelength of a particular clock signal.
Crosstalk may be eliminated or reduced by guard traces or routing 3-W.
Crosstalk may be eliminated by routing traces 3-W. This rule states that “the distance separation between these traces must be three times the width of a single trace, from centerline to centerline. For dual stripline, one trace is three times the width of its corresponding trace.
Schematic design of PCB projects 
