Start with the photo itself and the frame. Is the frame one of those folders that come from the photography studio or a regular frame the photo has been put in? If it is a folder, examine it carefully for the name of the studio. Next, very carefully, examine the edges and back of the photo itself. Sometimes you will find either the name of the studio, a location, or at least a logo. If you can figure out the studio, you can research that and try to narrow down both the location and the time frame in which the photo was taken. Both are important.
Now as to finding people who can help you identify time by dress and the like, start by locating an archivist. Is there a university or large public library near you? They may have an archivist. Or look for a local genealogical society. You may find someone there who can help you identify the time period of the clothing.
Other hints can be found in the way the photo itself has aged.
Look for a local photo restorer. They may be able to help you on that angle.
If you are good at noticing differences and similarities yourself, you can look at old vintage clothing website and maybe narrow it down some yourself.