I got two very useful parenting tips from this book (Boys adrift)
--The first was that boys tend (generalization, obviously) to not be motivated by the desire to please their parents and/or teachers. Just not a motivator for them.
I vividly remember the strong desire I had to make my mother happy as a young child, and so I was repeatedly frustrated by my son's apparent immunity to my feelings. I kept trying to manipulate him-- don't you care how I feel?-- but once I realized my approval didn't motivate him, it became easier for both of us.
--The second is that boys often thrive on competition-- competition IS a motivator. Competition has been removed from much of children's experience, especially in school, in favor of an "everybody wins" mentality. Many successful boys' schools divide the class into two meaningless "teams"--red and white-- at the beginning of the year, and frame almost everything into a meaningless competition between the teams-- to keep the boys engaged.
Now when I want my son to do something, I often present it as a competition-- for example if I want him to take pictures at the zoo, I will present it as a photography content-- and this works like a charm.