If you want to get started with your SSE you can find various guidelines that may inspire you. For example how to develop your vision, or which steps to take to build an SSE. Watch out for them. Be inspired by the previous experiences of others have. You will find a few hints here.
There are also concepts out there that are used for regular businesses. Why not just adapt them for SSE? For example take the “business canvas”-model or “super hero canvas” (Kieron, 2016). Of course in SSE we do not need any heroes or leaders, but the basic idea of the concept can be transferred to SSE. The “canvas method” helps you to ask major questions. It works like this: You find a number of important questions related to your SSE. Put them down on (only) one piece of paper. Take the time to consider these questions, to discuss them and – most important of all – to answer them. Do this together with others – with your future co-operative members, peers etc.