Here is the best article I have seen so far on how to make a DIY face mask. It discusses not only how to make the mask, but also the best materials and design features. It also ponders the limitations to protection. But most important, it describes how you should don and remove the mask to avoid contaminating your face and defeating the whole purpose of wearing a mask in the first place.

There is one design feature missing from the masks described here: they leave an air gap on each side of the wearer’s nose. Commercial masks often have a soft metal wire embedded in the upper edge that is easily shaped to close the gaps and achieve a better seal.

There is no way to “see” where the COVID-19 virus is, just as we can’t see other microbes. Healthcare professionals learn habits called sterile technique to minimize the chance of transferring invisible microbes from one patient to another, or to an open surgical wound. In the following video, the doctor demonstrates the use of sterile technique to ensure that the goods you bring into your home don’t carry and shed the virus.