Or, how to get a reader interested in your work. As far as I'm concerned you get one chance to make a first impression, and you should make it count.
Is it the most important part of a story? No. But it's rather like the first step into a large body of water. you put your foot in to test whether or not the waters are right for you, and if it's too cold, you might well decide not to go for a swim.
The first sentence should catch the eye and keep your attention, the same way that an elevator pitch should attract enough interest to get n agent or editor interested in your work. You have one chance to get it right. Why not make that first impression as memorable as you can?