Consistently available and going out of their way to provide feedback and encouragement where necessary.
The level of mentorship that you will receive as a graduate is partner dependent. Many are very hands on and proactive with grads, while others can be more hands off and let Senior Associates have greater contact with grads.
Several excellent mentors in the firm have taken a genuine interest in my career including some of the most senior and influential partners in Australia.
Management are friendly, open and approachable. There are structured performance feedback mechanisms, in addition to informal feedback given on an ongoing basis or at special request. I have been surrounded by industry leaders who, while busy, always make time to provide guidance and support.