Mac's don't need defragging as OS X automatically writes 2Gb or below sized files to one contiguous space on the drive. There are certain cases where's it's needed to free up a large spaces on the drive, but not something everyone has to do.

Far as other Mac maintainence, there really isn't any except to backup one's files regularly. Keeping Software Updated and run a web browser check to make sure the plug-ins are current.

Jan 27, 2020. Mar 30, 2019.

Clean your Mac’s keyboard. Our last but not least advice is to wipe your Mac’s keyboard. As you use your keyboard daily, it quickly gets dirty. Moreover, all those crumbs may live under the keys forever! If you were wondering how to clean Mac’s keyboard, there are no special rules here. Aug 05, 2020 Learn how to clean your Mac notebook computer. MacBook, MacBook Pro, and MacBook Air. When cleaning the outside of your MacBook, MacBook Pro, or MacBook Air, first shut down your computer and unplug the power adapter. Then use a damp, soft, lint-free cloth to clean the computer's exterior. Avoid getting moisture in any openings.

For Safari and Flash, this check is more accurate

Most of those cleaning programs are junk, especially MacKeeper.

If your friend got onto your computer and visited a bunch of adult sites, then I would recommend something like OnyX, doing ALL the cleaning and maintenance aspects and rebooting, perhaps followed by a Disk Utility Erase free space.

Best Cleaner For Mac Keyboard

CCleaner beta is out for OS X, used on PC's and combines cleaning and scrubbing of the drive if setup correctly.

Best Cleaner For Mac Laptop

If your interested in performance, read my post here

Best Cleaner For Mac Os