Buying your business and looking for financing by a bank, angel investor, buddy?  You need a business plan.

Selling a business?  One of the features of a good for-sale process is for the seller to be able to show the buyer a plan for the future.  It will help to wet the appetite of the buyer.

Operating a business?  You should have a business plan that helps to guide decisions, initiatives.

This article by someone who lives business plans, Tim Berry, is worth the read.  He gives great tips.

Business Plan Tips