Forbes recently asked its Agency Council what the best practices are to ensure a successful partner marketing initiative. Since we're a member, we contributed this:
Give More Value Than The Other Partner
Marketers typically approach these things worried that the deal will be uneven. If you’re concerned that the other partner will get more out of the deal or invest less—so they “win” and you lose—who cares? Set your own goals, but also try to give more than you take. Everything will go more smoothly, and that is a win in and of itself.
There are 14 more Best Practices here at the Forbes Agency Council website. Some pretty good ideas there.