There's the usual process which involves saying "hi" to the team, setting up their workstation, understanding their first project, etc... But one of my favorite additions has been a first-time full product walkthrough while the new designer records all of their least and most favorite parts of the experience and any ideas they may have.

A new candidate has a fresh set of eyes. More importantly, they have a fresh set of designer's eyes. There's something special about a designer's first impression, and you should take advantage of that before they're accustom to the product and all of its flaws.

Further reading: http://joshuasortino.com/journal/savoring-first-experiences