Q My Mac currently only has Stuffit Expander installed, so I cannot compress files into archives. Which compression utility do you suggest that I use?
A Your Mac already has a powerful, accessible, and free tool which you can use for most purposes: Archive Utility. Apple hides this away in /System/Library/CoreServices/Applications, from where you must not move it. One good way of making it easier to use is to place it in your Dock. It offers both Zip and GNUZip compression techniques, which you can select in its preference dialog. Drag and drop a file or folder onto its Dock icon, and a compressed archive will be produced for you.
If you want further improvements in performance, and slightly better compression ratios, then using a more modern format such as RAR or 7zip might be better. The App Store has a good selection of tools, including 7zMaster, which is generally one of the better performers, and Entropy, which also works well. Stuffit has seen better days and is relatively costly, so is probably not going to be a first choice.
If you need to compress particular types of media file, such as images, audio, or video, then specialist compression tools will generally be much superior. Further details are here.
Updated from the original, which was first published in MacUser volume 28 issue 10, 2012.