Printed Circuit Board (PCB) Tips

Tips on how to properly design/layout a Printed Circuit Board (PCB)
Sections

    General tips
        Make important nodes accessible
        Give space between components
        Place components with the same orientation
        Print the layout to see if components' sizes match
        Exchange wiring directions between layers
        Select the width of lines depending on current
        Know the specifications of the manufacturer
        Avoid 90º angles with traces
        Use the silk layer
        Use the schematic vs. layout comparison
        Create a ground plane
        Place bypass capacitors
        Route the differential signal traces in parallel
        Consider spots of heat
        Make parallel footprints for hard to find components
    Tips for power circuits
        Keep power and control grounds separate
        Use an inner layer for the control ground
        Make power traces wider to withstand higher currents
    Tips for mixed-signal circuits
        Keep digital and analog grounds separate
        Protect analog grounds from noise
    Tips for PCB mounting
        Solder from small to large components
        Be aware of cold solder joints
        Use flux for easy soldering
        Do not trust the multimeter continuity test

General tips
Make important nodes accessible

It will eventually happen that you are trying to figure out why something is not working and you want to measure a signal inside your PCB. Before designing the PCB, you should think which points will be important to troubleshoot your circuit and, in case they are not easily accessible, add a test point somewhere connected to them. There are various forms of test points, but the ones that form a loop are great for test probes with hooks.

Read more https://forums.autodesk.com/t5/eagle-forum/how-to-select-a-group-in-pcb-and-delete-the-selection-in/td-p/9110773