I have installed Ubuntu 13.10 and selected the option to automatically log in to my account when the laptop starts.
But now I want to change it so it asks me for my password when it starts. I can't find any option for that.
Open the System Settings application, then click on the User Accounts icon. In the top right corner, you will have to unlock the setting. Once unlocked, select the user on the left, and turn Automatic Login off.