Using Synchronization Software
Like all important data, you should also back up your projects regularly. This is not very difficult, since all data that has been inserted in a project is stored in one main folder. You can find detailed information on this in the article Structure and Content of a Project's Data Set.
The easiest way to back up a project is to copy the entire main folder of a knowledge area, including all its sub folders and files, to a backup medium using Windows Explorer or another file management program. The project should be closed at this time.
Using Synchronization Software
For extensive projects, the time required for backups can be reduced considerably if you use special software for this purpose. This makes it possible to back up only those files that have changed since the last backup. Free or inexpensive products for this are for example: Synctoy or Synchredible. Also with this variant the project should be closed during the backup process.