What type of character are you interested in writing about? Sometimes, characters define the settings. A story about a showgirl, a nuclear physicist, or a samurai warrior will take place in a location each is most likely to be found---Las Vegas, a science lab, such as Lawrence Livermore in Berkeley, or in 17th century feudal Japan respectively.
When does the story take place? Is it contemporary or does it take place in the 17th century? Time periods will have specific settings. For instance, 17th century Japan is a greatly different place than 21st century Japan.
What is your story about? Determine your fiction's plot and story, then outline it. Does the story require different settings, locations, or time periods, etc. in order to advance the plot? If so, what do you think they'll be? If your story is about a family, determine each character who will belong to this family, then visually move them in different settings you think they will likely go. For instance, where does the husband and wife work? Where do the children, if they are young, attend school? Where do they live? Do they take summer vacations? Where to? Do they attend church, synagogue, mosque? Do they belong to after school curricular activities or jobs, bowling or baseball leagues, charitable organizations? Each of these questions, for instance, will give you an idea about what type of settings you'll need to create for your story and how your characters will interact in them.
An old writing adage goes: write what you know. In this case, your hometown or region can be an appropriate place to set your story. Writers such as John Steinbeck, William Faulkner, Toni Morrison, Zora Neale Hurston, John Edgar Wideman, and others all used their hometowns or the regions in which they lived as settings for their stories. But don't limit this to regions or hometowns. Any school you've attended or job you've worked at; a particular store or bar you've shopped at or frequented; a neighborhood, church, or house or apartment you've lived in can all be sources for your fiction's settings.
Fictional places can also make great settings. If you're writing fantasy or sci-fi or even if you're writing literary fiction, then you can create your own settings for your stories. Be as detailed as possible in creating your fictional universe. Let the reader believe that the place you are describing actually exists. Determine what type of setting will work best for your story. If you're writing a space opera, then a colony on Mars might be the best setting for your story. If you're writing about office workers or university students, then create a fictional corporation or university for your setting.