1. Change passwords for accounts on your phone.
2. Beware of scams! Don't share personal info about your phone.
3. Use 'Find My iPhone' to locate your lost iPhone.
4. Get a replacement phone from your carrier (if needed)..
5. Report the theft to police. Get a police report.
6. Remotely wipe data to protect privacy on your phone.
7. Back up regularly to avoid data loss on your phone..
8. Consider a mobile device management (MDM) tool.