The best way to start a story is to make a strong impression without giving so much away that the rest of the narrative feels underwhelming. A good beginning offers a preview of all the story's important elements, such as characterization, conflict and style.
Professional writers have differing opinions on how to begin writing a story, but for less experienced writers, the most important factor is to simply start writing. Once those first words are on the paper, it's easier to keep moving forward. First drafts are not expected to be perfect, and revision is a key part of writing.
Sometimes it's helpful to imagine a scenario or a small group of characters as an exercise in beginning a story. Visualizing the scenario, drawing the characters or role-playing their interactions can send the mind down new pathways and inspire the storytelling process.
Some of the most memorable story openings place readers directly into the action. Memorable openings also contain a kernel of mystery or doubt that keeps readers interested. Stories that begin long before the action or include a lot of explanation are less likely to grab the reader's attention.
Reading the stories of accomplished writers is always instructive because it shows what works most effectively, but it is important to avoid letting the more famous writer become too great of an influence.