Start by defining the MVP. Review and cut scope until it truly feels minimal. Software is never done. We are OK with shipping things that aren't perfect. We can always ship another PR to improve it. Always be unblocking. Make it easy for people to be contributing at all times (even if alone in a separate timezone). The project plan starts minimal and evolves as we ship code. Invite others early to give feedback, incorporate that into the plan as the project progresses.