Although there is no guarantee, a good layout starts with a good schematic. Be thoughtful and generous when drawing a schematic, and think about signal flow through the circuit. A schematic that has a natural and steady flow from left to right will tend to have a good flow on the board as well. Put as much useful information on the schematic as possible. The designers, technicians, and engineers who will work on this job will be most appreciative, including us; at times we are asked by customers to help with a circuit because the designer is no longer there.
What kind of information belongs on a schematic besides the usual reference designators, power dissipations, and tolerances? Here are a few suggestions that can turn an ordinary schematic into a superschematic!
Add waveforms, mechanical information about the housing or enclosure, trace lengths, keep-out areas; designate which components need to be on top of the board; include tuning information, component value ranges, thermal information, controlled impedance lines, notes, brief circuit operating descriptions
