A strong opening creates an honest expectation about the story being offered.

An opening is a promise about tone, pace and subject, whether or not you meant to make one. A reader told by the first page that this will be funny, or frightening, or slow and interior, settles into the right posture and is generous from then on. Trouble comes when the opening sells something the rest has no intention of delivering. People are not disappointed by what arrives; they are disappointed by the switch.

Read your first paragraph and ask what it quietly guarantees. Then check whether the rest keeps that promise. An honest opening loses a few readers early and keeps the others.