Although PCB silkscreen layer does not play any role in the actual PCB work performance, proper PCB design can bring much convenient to manufacturing and troubleshooting process.
Another thing to consider when soldering PCB silkscreen layer is text placed under components. Although the component reference or part number placed under the component may still be useful during assembly, it will certainly make things difficult when troubleshooting after a long time. Some components libraries have the orientation marks placed under the components because they are used to properly place the part for soldering.
Although some circuits also have an orientation marks, to add one in the form of a triangle or a circle to make it as easy as possible to find the desired component orientation is still a good idea.
When using a large pin count device, additional marks (such as lines with pin numbers) can be added to the PCB silkscreen layer. It is common practice to place polarity marks on the outside of the component footprint, for components such as capacitors or diodes.
The resolution of silkscreen printing is not always as accurate as that in the actual PCB manufacturing process, so you should allow a few mils of tolerance, especially in high density designs. This is especially true when talking about placement markings, as these markings may sometimes overlap with solder pads and then cause electrical test failures or soldering problems. The recommended distance between solder pad and marking print is at least 6 mils (0.150 mm).
It is worth mentioning that, although various colors and fonts for you to choose from for your PCB silkscreen, most manufacturers can provide you non-standard options, but you need to pay extra cost.