This document outlines lessons learned from developing MoodSwings 2.0, an online intervention for bipolar disorder. It recommends having a solid development plan, keeping the intervention simple, budgeting carefully, limiting assessments, clearly defining responsibilities, setting realistic deadlines, shopping around for developers, communicating well with developers, testing thoroughly, and carefully planning recruitment. The most important research findings were about developing effective online interventions, while the most important knowledge exchange learnings involved understanding project management best practices.