How to report something broken

The difference between a bug I can fix today and one that sits for a week is usually four lines:

• What you did — "tapped the bell icon on the community page"
• What you expected — "the notifications list"
• What happened — "nothing, then it scrolled back to the top"
• Your device — "iPhone, Safari"

A screenshot beats all four. If you can only give me one thing, give me that.

"It is broken" is welcome too. I would rather have a vague report than none.