A founders shareholder agreement, also known as SHA (in some cases in the U.S. referred as a stockholders' agreement) is THE key tool to use to get your startup team to commit to the shared venture as co-founders - to start making your startup more than just an idea or a dream. Use it as a tool and a foundation of your startup venture, to move it beyond ideation (-2) or concepting (-1) phase to commitment phase (0). It will have a big impact on your startup credibility and valuation.
Link to original source: http://www.startupcommons.org/founders-shareholder-agreement.html
Startup Development Phases is free to share communication tool to help understand startup journey, identify key stages and to help develop Startup from "idea to business" and from "founding team to organization" in balanced and understandable manner.
Link to original source: http://www.startupcommons.org/startup-development-phases.html