When beginning a story, one must start at the beginning and also when revising this is a good place to begin. You want these opening lines to draw the reader in to read what you have written. There are some things to look at.
When I began writing I often started the book and finished the rough draft and went back to revise. One thing I had trouble with was finding the right place to begin. I often had to restart the beginning, sometimes in a different place or from a different character's eyes. Another problem I had was starting with descriptions of the character or the setting and forgetting about what would draw a reader inside. One bit of advice I heard from a writer years ago was to begin either when a change is about to happen to a character, in the middle of the change or moments after the change has occurred. Of course in the opening, you do need to give the reader a senseof what the story will be about and the genre you're reaching for.
The length of the opening matters. Too much description of places or people make the reader scratch their heads. Or to open with a huge cast of characters all talking about something can confuse the reader. Whose story are you telling? Another kind of beginning starts with the character waking up. This can be fine but going through every moment of him or her getting out of bed, going to the bathroom, dressing and you get the picture can bore the reader.
Overdoing the opening. Writing and re-writing the opening scene of a story can suddenly amke this too long and too detailed. I once had a writer friend who came to critique group and read the same opening every day for nearly a year. The opening had gone from a few pages to about fifty. Didn't leave a lot of room for the rest of the story.