How to prevent an OS X application from opening at Startup

From ArticleWorld

If OS X takes too much time to start up because of an application, or you feel that a certain application opened when you log in is not actually required, you can stop it from loading at startup. Here is how to do it:

Procedure

1. Go to the System Preferences of your computer. In the System section, select "Accounts" (bottom-left corner).
2. Select your account and click on the Login Items tab.
3. Select the application that you want to remove and click on the "-" button at the bottom of the list. The application will not be opened the next time you boot your computer.

Notes

Unlike many other operating systems, OS X does not hold the system-critical applications in that list. However, make sure that you do not disable an application that is required to be running before other applications. Doing so may prevent them from running and sometimes they do not display the most helpful error messages.

You should refer to the OS X documentation for details on how to prevent system-critical applications from starting up, but this is not recommended. Contact your system administrator if you feel that a certain service should be removed.