Maintain an active forum.
Most affiliates want to belong to a “community”. They want a place where they can hang out, swap ideas, ask questions and feel like they are a part of something. By creating your own affiliate program forum, you’ll give your affiliates just such a meeting place.
And when you (or your affiliate manager) actively interacts at the forum, you’ll be able to get affiliates visiting often. Again, this increases awareness, and awareness increases action.