Written for any new Apple iPhone owner who is keen to sell, freecycle or recycle one old iPhone... or more.

Before handing your old iPhone on, it is important to protect yourself from any privacy or related security threats that may result from the misuse of your phone's information. In the rush to freecycle my iPhone 1, I have seen first-hand how easy it is to overlook the removal of some important sensitive details (ranging from email and wireless account information to my routine calendar events and research voice recordings). Fortunately, I slowed myself down long enough to spot what I hope are almost all risks. So, the first action you should take is to accede to the old maxim "act in haste, repent at leisure" and set aside time in your schedule to prepare your iPhone for handover.

N.B. Before you begin the preparation, you should consider syncing your new iPhone via iTunes to ensure your SMS, network settings, et al. are transferred to the new phone, before deleting them off the old!

Your handover preparation should initially involve a full exploration of your phone's settings, its applications and their content and settings to identify information that could be sensitive. This will enable you to have a better understanding of the amount of work you may be required to do and whether you even have time to do it! In my case, I did a not-so-leisurely review in which I spotted over ten types of sensitive information that should be erased:

1. Financial and banking transactions listed under SMS notifications;
2. Private SMS correspondence;
3. Account and other information saved under personal and professional contacts;
4. Confidential professional and personal emails;
5. Private photo albums and un-downloaded pictures;
6. Webpage viewing history, web cookies and bookmarks;
7. iTunes store login details and user history;
8. Information stored by applications; 
9. Private notes under Notes;
10. Calendar events (particularly those show one's personal routine); 
11. Personal map locations (PINs that might show confidential locations);
12. Email account settings;
13. and wireless account settings.

My next actions were to go through each application at a time and delete their information. Since my jailbroken iPhone runs an old version of Cydia and OS 1, I was limited in the options I could follow to erase data: for example, I could not use iTunes' backup functionality to delete SMSs en-masse, nor Cydia's apps (like "Delete All SMS"). This means that the steps I took below are likely to be more lengthly than someone using OS 2, or greater, or Cydia's current version.

SMS
This was probably the most frustrating aspect, as Apple does not allow bulk deletion of SMSs. As Charlie Brown would say when faced with deleting four years worth of SMSs,  "AAUUUGGGGHHHH!" The best I could do was to (1) delete conversations, (2) delete individual messages and (3) ignore non-sensitive SMSs.

Photos
Even after deselecting the photo syncing option and running a sync, my photos were still on the iPhone. As a work-around, I selected the option "sync select albums", but did not choose any photo album. After running the sync, iPhone's iPhoto app then opened up with a pleasing "no photos" message.

Contacts
Similar to erasing my photos, I had to do a special type of sync to erase almost all contact details. After creating a group, I selected the "syncing to a group" option. After syncing, this cleared the many contacts that were not in that group.

Calendar events

Email
This was simple; once I deleted my email accounts, the emails linked to them were cleared.

Notes
After checking that I had indeed emailed all notes to myself, I deleted all notes.

Browser cookies, bookmarks and browsing history
I used preferences to clear my iPhone Safari browser's cookies and cache history. I then used the bookmarks organiser to delete all my potentially sensitive ones (for example, banking and investment sites and those used for social networking and self-publication).