iOS has many preference and configuration files where it stores tons of data that may turn valuable during an investigation. This section provides you with a detailed (although not exhaustive) list of some of those files that are useful to keep in mind:
/private/var/root/Library/Lockdown/data_ark.plist. This contains various information about the device and about its account holder.
/private/var/mobile/Library/Accounts/Accounts3.sqlite. This file contains account information.
/private/var/mobile/Library/DataAccess/AccountInformation.plist. You'll find account information used to set up apps here.