The iPhone's address book, which is accessible through both the Phone application and the Contacts application, helps you keep all of your contact information organised and easily at hand. But what if you want to enter information that's not just a name, address, phone number, or e-mail? Here's how to bring some potentially useful fields to light.

In any address book entry, click the Edit button in the top right-hand corner. You'll notice that beneath each respective section (phone, e-mail, address, etc.) it now offers to let you add another entry of that type, handy for distinguishing between work, home, and mobile phone numbers, for example.

However, if you scroll all the way to the end of the entry, you'll find a field right above the 'Delete Contact' button named 'add field'. Tap it and you'll be taken into a new screen where you can add a number of additional fields, such as prefix, suffix, nickname, job title, department, and even birthday.

One of the handier fields you can add is a generic date field, in which you can enter custom labels (your anniversary, for example, or a friend's kid's birthday) along with a date - it'll even sync back to your Address Book, just as you'd expect. There's also the ever-useful notes field, in case you need to add some information that doesn't quite fit in anywhere else.

Unfortunately, there is one downside to entering birthdays-they don't automatically show up in the iPhone's calendar application. For that, you will have to create a calendar event that repeats every year.