How to Stop an Application from Opening at Startup With Mac OS X

When you start up your Mac, a number of things happen—drivers are initialized, resources are allocated, and applications are automatically launched. Sometimes, you have asked the application to do this. Other times, the application sets that automatically when you install it. If you want to disable an app from launching every time you start up, follow these steps:
STEPS

1

OPEN THE SYSTEM PREFERENCES OF YOUR MAC. Click the Apple menu (?), then select SYSTEM PREFERENCES...

2

CLICK THE USERS & GROUPS ICON. It's at or near the bottom, in the SYSTEM section.

3

CLICK THE LOGIN ITEMS button. It's located above the right pane, next to the PASSWORD button. It will list all the applications that run on startup.

4

SELECT THE ITEM OR ITEMS YOU WISH TO REMOVE FROM THE LIST. Click the "-" button at the bottom left of the application list.

5

THAT\'S IT! The application will disappear and not run on your next reboot.
TIPS
You may need to unlock the Keychain to do this or provide your admin password to do this. If necessary, click the little lock in the bottom left corner and enter your administrator Name and Password.
You can also _add_ startup items in the Users & Groups window, if desired. Instead of clicking the "-" button, click the "+" button. Chose your startup item, then click the ADD button at the bottom right of the dialog.
Newer versions of OS X let you pick up where you left off after you shut down. To disable this, uncheck the "Reopen windows when logging back in" checkbox in the restart or shutdown verification dialog.