There are several posts that deal with this, and have dealt with it recently -- you might want to check out the Deans/dept chair thread. Here is one to start with: http://chronicle.com/forums/index.php/topic,87565.0.html
If you interact with the interim, recognize that he or she might be your competition. A good school won't have you interact with your competition, but there are many schools who aren't cautious in this matter.
Those are a few random thoughts that come to mind -- hope they help.