Before creating any AddressBook entries, you will first need to create one or more categories or groups to put them in. You may for example wish to have separate Personal and Business categories, and then within the Business category, to create categories for different types of client or customer.
It is worth a little thought to begin with so that you do not end up with inappropriate categories. For instance, if you are using the AddressBook to store names of hotel guests, a first thought might be to differentiate between guests according to year, and have categories such as 2006guests and 2007guests. While this has some advantages, some guests may come back year after year and it may be better to organise them in alphabetical order. Neither solution is right or wrong, but it is worth thinking which might prove to be the most convenient in the long term.
Later the SDK could be used to add another attribute, such as year they first booked, and the index operation used to organise them according to this date.