Here are a few tools we have found useful in the earliest stages of developing a new business. The SCORE National template gallery has many, many tools and templates as well.
A list of all NH and VT resources available to the local business owner.
A Business Plan is not a "one-time" document just for obtaining investors or financing. You should consider it to be a "living document" which you will update and upgrade from time to time as information and circumstances change and as appropriate as you thus make changes in your business.
Before you launch into your own business, there are dozens of details to be considered - from the momentous to the almost (but not quite) trivial. Here is a checklist covering many items you need to take care of.