Amazon begins temperature checks and will provide surgical masks at warehouses

Do not wear your face mask like the gentleman front and center in the photo! Not covering your nose has become the source of many memes but it still widespread. Simply having the fabric on your face does not grant you a protective aura.

The primary purpose of everyone wearing masks is so that people who are asymptomatic or pre-symptomatic minimize the spread of their droplets to everyone else. If the mask also protects you from sick people, that is an added benefit but secondary. Only N95 masks worn properly can guarantee protection for the wearer.

That means covering the mouth is most important because even breathing releases droplets. And the nose should be covered too, but only covering the mouth does help.

[edit after re-reading parent comment]

This article offers some links and data on the effectiveness of even homemade masks at filtering particles:

https://smartairfilters.com/en/blog/diy-homemade-mask-protec...