It was in a public speaking class where I learned the importance of the opening line and I think it applies whether you're speaking or writing.
Whatever it is, your opening line should make that person seated in the last row in the auditorium ignore whatever it is they're thinking about—or doing— and look up and listen. And it's the same with your writing.
Grab your reader's attention with your first sentence.
One that makes them want to read the next sentence and then the next, until there are no more to read.
Not sure how to get started? Let me know if I can help.