If you go to your contact manager (in the left-hand tab, hit Contacts & Leads > Contacts). Here you can view a list of all your contacts. If you double click on the contact's name (which is in a blue box) and scroll down to the section that says, "Custom 1, Custom 2, etc." you can manually make lists that way and name them whatever you would like. Or you can go to the Category section and select a category from the drop-down menu.