This is the simplest method and ideal for novice users. The process is to create a duplicate (or zipped archive) of the entire Unity project folder. Some users report exporting the project game assets into a package as a solution for backups. While this is helpful for moving assets between projects, there are various project settings that are not retained within a new package.
Ideally, whichever local backup method you use, the resulting backup archive should be transferred to a separate drive for safe keeping.