In scripts, you can use Get ( AccountName ) to get the current user's account name. You can set up a table where one field is the user's account name and other fields hold their contact information.
If you use a field holding an account name to identify who "owns" a particular record, you can perform a find to pull up all records with that account name. You can script this and use File Options to run this script when the file is opened. You can define such an account name field to auto-enter the current user's account name when the record is created as a way to automatically link records to the person who created them.
You can also use Manage | Security to restrict user's ability to view and/or edit records not marked with their account name. To learn more about this approach, see "Editing record access privileges" in filemaker help and pay particular attention to the section titled "Entering a formula for limiting access on a record-by-record basis".