If you want to enable Automatic Login mode, create a non-Administrator account to use. That way, even if someone does get access to your Mac, they won’t be able to use the Administrator account. Of course, you might have to log out and then log back in as the Administrator, but this strategy provides a good compromise between security and convenience.
To configure the Automatic Login mode, use the following steps:
Open the System Preferences utility.
Click the Accounts icon to open the Accounts pane of the System Preferences window.
Click the Set Auto Login button. The login account sheet will appear. By default, the username of the currently logged in account will be entered. If you want to have the current account logged in automatically, skip to Step 5. If you aren’t logged in as the Administrator, you will have to authenticate yourself before you can make these changes (click the Lock icon, enter an Administrator User Name and Password, and press Return).
Enter the username for the account into which you want to be logged in automatically in the User Name field.
Enter the password for the account that you want to be automatically logged in when the Mac starts up.
When you have entered the user account information, click OK to enable automatic login. When you return to the Accounts pane, you will see the “Log in automatically as username” check box where username is the account you selected in Step 4.
The next time you start or restart your Mac, the account you specified will be automatically logged in and you will move directly to the desktop for that account.
This setting affects only the start or restart sequence. When you log out instead of shutting down or restarting, you will still see the Login window again and will have to log in to resume using the Mac.
To disable automatic login again, uncheck the “Log in automatically as username” check box on the Accounts pane.