I heard a speaker talk about business plans and its relationship to start-ups this past weekend.  He was advocating axing them and focusing on the business at hand.  Further, he stated,  that they are often imposed on us by someone that has never started a company.   I am sympathetic to his thoughts.  Planning is essential to start-ups.  Decisions though are often made based on new data and changing circumstances and understanding.  So I believe planning or better stated creative strategic thinking is essential - but often it is informal and not documented.   Of course,  if someone requires 'the plan" for you to access capital,  you have to jump through the hoops.  But  I would not recommend putting together the 20 - 30 page formal plan for yourself before you get started.  Think like crazy - talk to lots of people - get input - but jump in!  No plan is ever executed perfectly because there is just so much change and dynamics in the start-up process.   Another speaker said it well - a birthing room has pain,  it is bloody,  there is lots of movement and action - you are birthing a company.  The well organized, things laid out perfectly, and implemented according to a specific plan is the cemetery.   Be part of a company birth - expect lots of ongoing challenges and dynamics that you will need to respond to.  Often quickly.