To make sure everyone on the project has the same vision of who you're building for, create a single picture of "the user." Assumption personas are fast to create and easy to verify later.
How do you turn data from site visits and other user observations into something coherent you can use to guide product development? Create Experience Maps and extract pain points and user goals!
I'm sharing the early-stage user centered design techniques I use with clients in a series of courses on Lynda.com. Each of the quick courses covers a different technique. Taken together, they should give you a solid set of tools for iteration zero.
We often overlook one of the biggest benefits to following user centered design techniques. Good user centered design is great at turning empathy-based concepts like users’ thoughts, feelings, frustrations, and desires into something systematic that development team members can use to build products.