sessions

Hi there! How can I track users with sessions, without using passwords or logins? I want the user to use a shopping cart, to create custom tables, etc, but I will never ask for his personal info or his credit card, so I don't want to require a registration, but I still wnat to track the user from the moment que enters the site to the moment he quits. Is that possible? Is there any tutorial available just for this? Thanks in advance! Daniel Brazil