Create your board frame on a 0.05” grid. Make the lower left corner start at 0,0.
Usually the board frame is rectangular. For specific reasons you could also do other types of shapes such as polygons.
Stick parts on a 0.05” grid. You should not break this rule unless you have a very good reason.
Any LED should be labeled with its purpose (power, status, D4, Lock, etc).
Idem for connectors: e.g Vin, Port1, Batt, 5V, etc.
Idem for pins where applicable: e.g TX, Power, +, -, Charge, etc.
Idem for switches and switch states: eg. On, Off, USB etc.
When applicable, it is better to avoid having vias go through the silkscreen when adding labels.
Group components together. For example the resistors surrounding a transistor in your schematic will also be grouped together on the PCB.
Minimum drill size should be 15 mil.
Minimum annular ring size should be 7 mil.
7 mil is the minimum size for traces. 8mil is acceptable. When possible try to keep the traces size to 10mil.
Use thicker traces for power lines. 12mil=100mA max, 16mil=500mA max etc.
7mil between traces and space is reasonable.
Avoid 90 degree corners. Straight lines with 45 degree corners are preferable.
Where applicable use a ground pour on top/bottom layers.
To prevent pours from shorting to traces make sure you use a 10mil isolation setting on any of the ground pour.