Here are some important layout tips and guidelines for an efficient and well-functioning PCB.

1. PCB Trace Spacing: Leave adequate space between traces. Packing pads and traces too close together increases the risk of creating a short circuit if traces accidentally connect during PCB manufacturing. 
2. Trace Angles: Avoid using 90-degree trace angles. During PCB fabrication, there is a chance that the outside corner of a 90-degree trace is etched narrower than your standard trace width. So, try to use 45-degree angle traces.
3. Widen power and ground traces. Wider power and ground traces allow for more current to flow through them and reduce heat build-up, which could otherwise damage your board and wires.
4. Dissipate heat using vias. Vias provide electrical connectivity between layers. But thermal vias can act as a pathway to move heat away from heat-generating components to an area where it can be dissipated.
5. Add Fiducial Marks: Add fiducials to the same side of the PCB where SMT parts are to be placed. Surface mount assembly machines use fiducial marks to ensure the correct orientation of the PCB, which is necessary for component placement.
6. Use power planes to distribute power to nearly all areas part of the PCB. You can create power planes by adding copper layers to the stack-up and connecting them to power or ground.