herpderp,
There isn't a specific thing you need to do as it is based on how the system is configured.
In any case you need to make sure of the following things that tend to always need to be done.
1. Change the Description on the phone in the LastName, FirstName format, don't forget the space after the comma.
2. Change the Username on the phone in the FirstName Last Initial format or whatever you normally want people to see when that person calls them.
3. Change the passcode of the phone IF the user is going to need to do any remote changes on the phone, such as using the Configuration Assistant.
4. Delete any old personal keys on the phone.
5. As for the mailbox I usually tell the customer to delete the old one and create a new so there isn't anything left of the old users personal information.
6. Add the email address in the MB if they have Unified Messaging.
7. Delete and recreate the Users programming if they Dynamic Extension.
After that you just need to make sure the phones are in the correct call flows such as Extension Lists, Hunt Groups, Page Zones and CO Trunk Groups Outgoing Access if necessary.
Thanks,
TE