Maybe to be more clear, 1 FM File into ANother
There is no fast, efficient way to do this. Tables (both structure and data) can be imported, but relationships between table occurrences cannot be imported. Scripts can be imported, but may need repair after import due to referring to other parts of the database, such as a layout that does not yet exist in the new file. Layouts can be copied and pasted, but this also can require additional "fixing" after the paste to get all elements up and working. Value lists cannot be copied and pasted nor imported, though you can copy and paste the custom values from one value list definition to another.
And FileMaker Advanced's Database Design Report becomes very helpful in getting all the parts correctly reconnected.
Here's one thread that describes the layout duplication part of this in more detail: Importing Layouts