best way to delete old orphan files

Use the Finder, by dragging those files to the Trash.

Please read OS X El Capitan: Increase disk space.

AppDelete will do both. It properly and completely deletes apps and finds and deletes orphan files. I've used it for several years without any problems.

Hello Rosettazawc,

You can use Disk Utility to erase your hard drive. Then reinstall the OS. Then migrate over only user documents or rely on iCloud for migration.

Unfortunately, OS X has no installer/uninstaller architecture. This is really the only reliable way to clean up these orphan files. You can download and run various "app zappers". They will delete many files. Hopefully they won't delete too many and wreck your system. They will never remove all files.

If you start with a clean system, you could use the wonderful "Suspicious Package" from Mother's Ruin Software (http://www.mothersruin.com/software/SuspiciousPackage/). But again, there is no way it will detect everything. There are always apps that will auto-update.

Hi rossettazawc OmniDiskSweeper is a good tool to use for deleting old and moldy files.

https://www.omnigroup.com/more

Omni DiskSweeper can show you the precise size and location of all your files. It will inventory your whole disk starting from the files. If you want you can even delete files from OmniDisk Sweeper. But be careful some of the items may be important to your system

If you are doing it by hand, here are common places to check.

System Preferences > Login Items > Users & Groups > Login Items

~/Library/Preferences/

/Library/Preferences

~/Library/Preferences

/Launch Agents

~/Library/Launch Agents

/Launch Daemons

~Library /Launch Daemons