To identify a file without an extension, users are advised to check the file properties for clues about its origin and name. Utilizing a hex or binary editor can provide insights by revealing the file's header information, which often indicates its format. If the format remains unclear, researching various file types online can help. A trial-and-error approach is also suggested, where users can create a copy of the file, change its extension, and attempt to open it with different applications. Caution is advised, as there is a risk of opening potentially infected files. Additionally, examining similar files based on their names or modification dates may offer hints about the unidentified file.