Short, simple, descriptive and relevant to page content – with variations

Use a maximum 3-4 keywords in your file name and these keywords should be in your web page title as well.

Separate all keyword with hyphen rather than with underscore, that is a  “-” instead of “_”

user lower-case

Include major locations (like “Santa Rosa”, “Sonoma County”, “North Bay”)

SEO is per page not just site wide, so you can emphasize different things on different pages (i.e. installation vs equipment vs contact vs customers vs savings….)

Examples
solar-panel-installation-Santa-Rosa.jpg
solar-panel-installers-Santa-Rosa.jpg
solar-installation-NW-Santa-Rosa.jpg
PV-system-Sebastopol.jpg
Photovoltaic-equipment.jpg
Echo-Solar-best-equipment.jpg

Loretta-vp-solar-installations.jpg
Alan-installer-solar-equipment.jpg

Put yourself in a customer’s shoes, think of how they will search to find you, then sprinkle those in along with what’s relevant to the image/video/document.

Try this method:  Pretend that some people will never see the image, so you have to pick 4 words to describe it for them.
Pick one for each of:

• The noun (person, equipment, chart)
• The place (“Santa Rosa”, “Bay Area”…)
• The action (“installation”, “compare”, “buy now”, “contact”)
• One last word to tie it all together

SEO is mysterious, as it should be – so that we mostly focus on our content rather than trying to game Google.

Make human friendly file names and you’ll probably have picked one that’s SEO friendly as well.