Data collection fuels relationship building, while your mission drives it. Data collection is the necessary first step though. Just as foundations are thoroughly researched to ensure proposals will meet a welcome, the individuals who comprise donors, boards and foundation staff can be researched. This data collection is a sincere or insincere as you want to make it.
Over the past 3 years, I've developed a friendly relationship with the president of a local foundation. In between grant discussions, we discuss our families, share children photos, and talk about general issues related to our collective field. Consequently, we feel very comfortable working together or discussing possible projects, or knocking those projects out of the sky. This relationship doesn't guarantee successful grants mind you. She declined my last two proposals but we had great discussions about the reasons.
So you can start building relationships by talking with foundation staff and individual donors and remembering their interests. Establish a human connection. You don't have to like the person; you needn't become bosom friends. You begin by recognizing that these are human beings who share an interest in improving the social condition.
Is this relationship instigated by the potential for donations - Yes. But it needn't be insincere. It's the same type of relationship you may have with your primary care physician, or investment counsellor, or regular mechanic. Or they may have with you. We may need the funds controlled by foundations or donors but they need the programs and reputable organizations into they can invest those funds. If the outcome should improve the human condition, then the relationship should be (or perhaps "can be") something more than perfunctory.
it really depends on how you and the donor want to handle it.