Every project needs a solid plan.  This is also critical for starting a business.  We need more overlap (don't re-invent) between these two.

Project management has much to learn from Start-Up Business Planning.  Business Planning has way more history, literature, training, tools, templates, checklists, forums, etc. available that PMs can leverage (and often for FREE).  You would not believe how much business planning support there is from governments, universities, associations and generally all over the web.

In a project, we often focus too much on scope and requirements, and miss out on the things that a business plan does so well at planning for.

Below is a sample I use when planning a new business and I also use this as a guideline or plan for projects.

This can be seen as a table of contents for a Project or Business Plan.  It can take considerable effort to do it correctly.  However, if not enough time to delve into the details, then at least it should be considered and presented to senior management and executives, so seeds are planted and you are working towards clarity and common understanding of each section and priorities.

I like to start out with one thing, the CUSTOMER.  Then everything should build off that.  You need to create a culture within your team that also owns this, believers in it and aligns how they deliver with that kind of theme.