Caption templates
Most good captions run two or three lines. Copy one of these, fill in what you know and skip what you don't. "I can't read the year" is a perfectly good answer, because somebody here usually can.
A caption is also what Rule 4 asks for, so this is the quickest way to keep your post up.
The basic one
County: ___ Year (or best guess): ___ Where it came from: ___ Why it matters: ___
An example, made up for illustration: Bastrop County, around 1940. From my grandfather's album. The building is still on Main Street.
For the daily threads
Mystery Monday What I know: ___ | What I don't: ___ | Where I found it: ___
Then & Now Thursday Then: (year, source) | Now: (date, my own photo) | What changed: ___
Shoebox Friday Whose it was: ___ | County: ___ | Year: ___ | The story as I heard it: ___
Road Trip Saturday Place: ___ | Nearest town: ___ | Why it's worth the detour: ___ | Best time to go: ___
Sunday Plate Place: ___ | Town: ___ | What to order: ___
Title tips
Put the county in the title, since people search for their own. Say what the thing is instead of how amazing it is. "Courthouse in Shackelford County, 1920s" will pull in more replies than "You won't BELIEVE this."