I've just been through a classic example of how a manger should not handle their resignation and a new manager should not handle their introduction :)
My division is being restructured and the unit I was in was split in two to create two new units with differing responsibilities (one web and one words for want of a better way of putting it). The former head of the department moved across to manage the new web unit and a new manager was appointed to head the words unit. It is a public service organisation and the restructure was a "managed" process so we all knew this was going to happen. So no problems with that, however in the weeks preceding the formal split the head of the department basically stopped talking to anyone that wasn't going to be in her new team. About anything, no hello, no interest in the work the rest of us were doing, no nothing. In a unit of 13 people it actually takes a lot of effort to ignore 7 of them!
She wasn't a particularly inclusive manager and made no secret of having her favourite people and favourite things to work on so my being ignored was nothing new. But while we were all being told by HR and the Division director that it was business as usual and that until the formal split noone should be assuming or talking about new roles etc, my former manager was having discussions with her "about to be" new team about what they would be doing, having team meetings, talking to people about new roles that weren't open for application - all in an open plan office while the rest of us were sitting there.
To make matters worse, the new manager for my unit didn't/couldn't acknowledge she was the new head. Once the cutover date came it took her another 2 weeks before she spoke to the whole team. Admittedly because of the restructure she was involved in a lot of higher level discussions out of the office, but to not find 10 minutes in 2 weeks to get 7 people who sit within 3metres of each other together to say hello is as just poor form as the former manager not bothering to say goodbye to half her team.