How do I password protect my mac on startup?

As it is now I have my account and a guest account so I need to put in my password to get into my account but how do I password protect upon start up without having to have another account?

I don't understand what you're asking. Can you please be very clear?

I am asking how to change the settings so that when the computer starts up it requires my password to proceed. As of now at startup it shows the list of users. Me and the guest account. I choose my name and enter my password. However I prefer not to have the guest account active at all. Problem is before I activated it I was not prompted for a password at all. I would like to be prompted for a password regardless of if the guest account/other user accounts are active or exist or not and that was not happening. I am sure there's a way to do it that I have not been able to figure out. I messed with the various settings and so far the only way I could figure out to be prompted for a password is if there is more than one account in the list at start up. I want to be prompted even if my account is the only one that exists. Hope that makes sense.

Open System Preferences, click Accounts, click Login Options, click the lock and enter your password, select disable automatic login in the dropdown menu, put a dot in the "Name and Password" option, and then in the four options under that, make sure there's checks in the checkboxes for first two options none in the third and fourth ones..

Done! Thanks to both of you for your replies!

You're welcome.