How can I write professional captions?

Question

a professional caption for a professional photojournalist

Answer 1

Who: first last, job title, company/unit
What: specifically what they are doing that makes this picture compelling
When: Date
Why: why are they doing this, why is this special
Where: As specific as possible
How: how did they accomplish this task

Then add a sentence or two of extra information to better understand what is going on in the photo.