If you have a screen saver activated or if your computer is in sleep mode, you can immediately access your computer by moving your mouse or pressing a key on your keyboard. You can however require a password to access your computer in either of these two instances so that others will not have access to your computer when you are away.
To assign a password to your screen saver and to wake your computer from sleep:
1. Click the Apple Menu icon and click System Preferences.
2. Click Security under the Personal area.
3. Click the “Require password to wake this computer from sleep or screen saver” check box.
The next time you wake your computer from sleep or deactivate the screen saver, you will be required to enter in your account password. Using a password-protected screen saver in conjunction with Hot Corners (see post on Using Hot Corners in Leopard) allows you to immediately lock access to your computer before you step away.