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.
AppCleaner is a small application which allows you to thoroughly uninstall unwanted apps. Installing an application distributes many files throughout your System using space of your Hard Drive unnecessarily. AppCleaner finds all these small files and safely deletes them. Simply drop an application onto the AppCleaner window. How to clean Mac hard drive using Cleaner-App: 1. Launch the application; wait a minute for scan completion. Switch to each section to see your largest files, downloads, installer packages, screenshots, duplicate files, same name files, and photo series files. Select unneeded files from your Mac storage, and then click the Review and Remove button.
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.
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.
CCleaner beta is out for OS X, used on PC's and combines cleaning and scrubbing of the drive if setup correctly.
![Storage Cleaning App Macos Storage Cleaning App Macos](/uploads/1/3/4/2/134292934/481825005.jpg)
If your interested in performance, read my post here