In my personal experience, which mostly smells of roses I must admit, acts of selfless magnamity tend to inspire a similar response. Acts which appear to serve some ulterior purpose do not, and tend to in turn cause behavior which is somewhat more self-serving. The "trick" is how to display authenticity when trying to be magnanimous. Because of this, to get the other person to do what I want, I usually try to do what they want first. I rarely ask anything of anyone because I find it makes people more likely to help me in the long run. This kind of behavior has its own pit-falls, but it is a kind of non-verbal communication which people tend to listen to better than any argument I might be able to present.