RJ PHOTOVIDEO  Why? For maximum security settings on your computer, assuming you did create and set a password, do the following.

Go to System Preferences>Security. Check the boxes for Require Password To Wake This Computer From Sleep or Screen Saver; Disable Automatic Login; and Require Password to Unlock Each Secure System Preference. You may have to click on the Lock and enter your Password to enter your choices.

Then, while still in System Preferences, go to Accounts, and click on Login Options. Make sure that Automatically Log In As is not checked, and for Display Login Window As you will check Name and Password. Again, you may have to click on the Lock and enter your Password to enter your choices. If you did not create and set a Password, while in Accounts, click on Your Account in List, then click on Password tab>Change Password. If you did not ever enter a Password, this was left blank. Now you can enter a Password or change your Password here.

Now open up Keychain Access (Applications>Utilities), and open its preferences. Check the box for Show Status in Menu Bar. Now when you need to secure your computer, click on the Lock Icon in your Menu Bar, the first choice is Lock Screen. Selecting this will Lock your screen and start screen saver. To get back in, click mouse or any key, like Space Bar, computer will ask for your Name and or Password.   
(Version 1.0)

RJ PHOTOVIDEO  Why? For maximum security settings on your computer, assuming you did create and set a password, do the following.

Go to System Preferences>Security. Check the boxes for Require Password To Wake This Computer From Sleep or Screen Saver; Disable Automatic Login; and Require Password to Unlock Each Secure System Preference. You may have to click on the Lock and enter your Password to enter your choices.

Then, while still in System Preferences, go to Accounts, and click on Login Options. Make sure that Automatically Log In As is not checked, and for Display Login Window As you will check Name and Password. Again, you may have to click on the Lock and enter your Password to enter your choices. If you did not create and set a Password, while in Accounts, click on Your Account in List, then click on Password tab>Change Password. If you did not ever enter a Password, this was left blank. Now you can enter a Password or change your Password here.

Now open up Keychain Access (Applications>Utilities), and open its preferences. Check the box for Show Status in Menu Bar. Now when you need to secure your computer, click on the Lock Icon in your Menu Bar, the first choice is Lock Screen. Selecting this will Lock your screen and start screen saver. To get back in, click mouse or any key, like Space Bar, computer will ask for your Name and or Password.   
(Version 1.2)