SLIS Professor Howard Rosenbaum addressed this question in a presentation. His focus is in the context of web sites, but the ideas can be applied to any information planning needs. Below are excerpts (with the slide number). The full presentation "Fun with Information Architecture: Designing Web Sites that Work".
Think strategically
What are the relevant content domains?
Given the constraints what can be done?Plan
How are these domains related to each other?
What is the structure of these relationships?Design
What arrangement best supports the structure and organizational requirements?Manage
What people, tools, and resources are available?