Most OS X applications are completely self-contained "packages" that can be uninstalled by simply dragging the application to the Trash. Applications may create preference files that are stored in the /Home/Library/Preferences/ folder. Although they do nothing once you delete the associated application, they do take up some disk space. If you want you can look for them in the above location and delete them, too.

Some applications may install an uninstaller program that can be used to remove the application. In some cases the uninstaller may be part of the application's installer, and is invoked by clicking on a Customize button that will appear during the install process.

Some applications may install components in the /Home/Library/Applications Support/ folder. You can also check there to see if the application has created a folder. You can also delete the folder that's in the Applications Support folder. Again, they don't do anything but take up disk space once the application is trashed.

Some applications may install a startupitem or a Log In item. Startupitems are usually installed in the /Library/StartupItems/ folder and less often in the /Home/Library/StartupItems/ folder. Log In Items are set in the Accounts preferences. Open System Preferences, click on the Accounts icon, then click on the LogIn Items tab. Locate the item in the list for the application you want to remove and click on the "-" button to delete it from the list.

Some software use startup daemons or agents that are a new feature of the OS. Look for them in /Library/LaunchAgents/ and /Library/LaunchDaemons/ or in /Home/Library/LaunchAgents/.

If an application installs any other files the best way to track them down is to do a Finder search using the application name or the developer name as the search term. Unfortunately Spotlight will not look in certain folders by default. You can modify Spotlight's behavior or use a third-party search utility, Easy Find, instead. Download Easy Find at VersionTracker or MacUpdate.

Some applications install a receipt in the /Library/Receipts/ folder. Usually with the same name as the program or the developer. The item generally has a ".pkg" extension. Be sure you also delete this item as some programs use it to determine if it's already installed.

There are also several shareware utilities that can uninstall applications:
AppZapper
Automaton
Hazel
CleanApp
Yank
SuperPop
Uninstaller
Spring Cleaning

Look for them at VersionTracker or MacUpdate.

 

---

More on uninstalling software:

Application Bundles

Most Mac OS X applications (anything that ends in .app), like Safari and iTunes, are bundles. The application icon you see in Finder (typically the Applications Folder) is usually a special folder itself, made to appear as a single double-clickable file. These "folders" contain all, or at least most, of the files needed to run the application, ie they are self-contained. This means that to uninstall these applications, you only have to drag them to the Trash. If you control-click (or right-click) on an Application icon, and you see "Show Package Contents", then it is a bundle.

 

Additional Files

Applications will leave behind preference files, and sometimes application support files, neither of which are stored in application bundles. Preference files can be safely deleted, but they usually take up negligible disk space — and, if you decide to reinstall the application again later, keeping the preference file means your settings will still be there. They are stored in the Preferences folder within your user's Library folder (~/Library/Preferences), or may also be stored in the system-wide Library located at the root of the system volume (/Library/Preferences/).

Application support files can take up anywhere from a few kilobytes to several gigabytes of space, depending on the application installed. Examples of applications that have large support files are multimedia programs such as Garageband and DVD Studio Pro. They are located in the Application Support folder within your user's Library folder, or in "/Library/Application Support/".

To remove an application's icon from the dock make sure that the program is not running at the time, then simply drag the icon off of the dock and let go. There will be a puff of smoke animation and the icon will be gone. This will only remove the dock icon/shortcut, and will not touch the application itself or any of its support files

 

Using Finder to remove Application Bundles and Additional Files

To manually remove an application and all associated files:

• Launch Activity Monitor and change "My Processes" at the top to "All Processes", then make sure the app you want to remove is not running. If it is, quit the process before proceeding.
• Launch Finder and search for the app name (hopefully unique, such as Skype)
• You can narrow the search to specific folders or search your whole Mac
• Searching "File Name" vs "Contents" usually provides better results.
• Click the + button below the search term to add criteria
• Click the search criteria drop-down and select "Other...", then "System files"
• Click the "don't include" and change to "include"
• Sort by name, kind, date, etc. to identify components of the app, such as folders, .plist files, cache files. etc.
• Delete all files and folders related to the app.
• Don't empty your Trash until you've determined that everything is working OK, in case you need to restore something you deleted by accident.
• A reboot might be necessary to completely remove some apps.

 

Applications with Installers/Uninstallers

If you ran an installer to install an application, you may wish to try running the installation program again to see if an uninstall option is available at any point during installation (many times in a drop-down menu). Check the installation CD or disk image for the original installer file. Some vendors have included simple Perl scripts that will run in the command line to uninstall applications, and may be named "uninstaller.pl".