How do I uninstall a program completely on a Mac? I come from a PC background... every time I want to uninstall an application, I must use add/remove programs. On the mac, you can simply run a .app file from wherever you want, and many say that the way to uninstall them is simply delete this .app file.

However, I have noticed that many apps save files in the ~/Library/Application Support/ directory. So when I delete the .app file, all those files are retained in the Application Support directory. Isn't there any way to uninstall an app and have it remove everything it installed on my hard-drive?
You can use this free app:
AppCleaner
(Synium used to offer CleanApp, but the product has been discontinued. You can still download a demo version which supports OS X 10.8 Mountain Lion up to macOS 10.14 Mojave.)