The first one is always the hardest. And this goes double for sentences. You have submitted your book proposal and you’ve been accepted. You have an advance. The angels are singing. But where the fuck do you begin?
Novelists can at least write something arty. But nonfiction books are more difficult. You have to get to the point, you have to draw people in. Sometimes you write something cheesy just to get it out of the way.
This is fine. But you must go back and revise it. For example, “This is the most exciting era in underwater basket weaving! True, when the craft was first established a hundred years ago, it changed the way everyone looked at baskets and suddenly there were baskets in every house and over everyone’s arm, which magically made every person in the world become immediately organized. But now coed naked underwater basket weaving is everyone’s favorite joke sport! They mentioned us on SNL.”
No. This is not a good first sentence because you disprove its assertion in the second sentence. A world-changing phenomenon is more important than a joke on SNL. Maybe you can delete the first sentence and begin with the second.
I’m a fan of writing whatever the fuck you have to to get to the next sentence and thus the book. But! But! You must go back and change it in your second draft if it sucks. Far too many authors of lifestyle books and trade nonfiction let their first shitty sentences stand. And it’s not their fault. Often they are experts in their field, not in writing. They struggle to get words on the page.
It’s our fault. Editors need to make sure the whole book doesn’t suck and that includes the first sentence. A lot of times we are distracted by 200-word steps or securing rights to 500 photos, but we still need to look at the beginning and make sure it is compelling. Or at least be sure that it is not totally fucking embarrassing.