Sure. I'll echo some of the topics that Bruce has brought up and I'll add.
Fundamentally, I think you need to ask first. The first thing you need to do to start building any relationship is ask for the interest and then the formal consent. That can only be given by specific people within a community, so you need to ask who the people are who make the decisions. Who are the leaders who give the consent to go ahead with an initiative that might be information gathering to support a particular policy?
In addition to that, one thing I've been taught to do is to really make sure that the information needs and the questions from community are front and centre. That's asking what those questions ought to be and what sorts of data we should start collecting together. That's just it; it's the initiation of the trust and the building of the relationships.
I would love to pass the mic to my collaborator, K_ii'iljuus Barbara Wilson, who taught me a lot of that.