It has taken years of trust buidling to get to the level with our local LE and we are always only one new sherriff away from loosing that relationship.
It is an ongoing process.
In addition to your fielding excellently trained and certified teams (everything David says), they need to know
1) You are there for them and will not sidestep them and do your own thing.
2) You will
follow a chain of command and do what you are told.
3) You will not seek out the press, (PR
things ok, but not about any search, ever -if the press wants to interview you on a search ALWAYS go to the IC or their press liaison - offer to the IC to do a "how search dogs work" peice so the news folks can go home with something, but never say anything about the search itself - some of these folks are very tricky at trying to extract info)
4) If they have dogs, you accept they will work their dogs first. Actually shortly after the person goes missing their dogs probably are the best K9 resource because they do it day in and day out on fresh tracks .....
5). It is not alway about working the dogs, it is about finding the person and if they need you to go door to door to hand out pamphlets then that is what you do and you do happly. We had a find that way a few years ago. The dog was hot on his trail and would have found him, but he wound up on someone's front porch and they recognized the face from the flyers and called in before they got there.
6) Try to train with them if you can, even if it is just you hiding for them. I would not offer to take a bite but I know our LE has bloodhounds that will jump on you but not bite you.
7) Never just show up on their doorstep during a search.