There are two radically different types of startups, each with different attributes and needs.
Existing business model
Existing business model and the startup is looking to implement it. Opening a retail store or a restaurant is an example. Buying a dump truck and a backhoe and finding customers to hire them out to is another example. These types of startups typically become ‘lifestyle’ businesses. While they can be very successful, they are limited by the time, energy and resources of the founder.
For these startups, they should have a business plan and then execute it. The founder’s challenge is learning the skills of being an entrepreneur.
Unproven business model
The other type of startup is radically different. This is a founder with just an idea and a vision. The founder may be confident they know what the market wants, but the idea is unproven. There is no proven business model yet. If this founder prepared a business plan, it would be only the documentation of the founder ‘s unproven guesses. This potential entrepreneur needs a methodology to search for a business model.
The best resource for this type of startup is The Startup Owner’s Manual by Steve Blank and Bob Dorf.
On Steve Blank’s blog there is an incredible amount of links to resources for startups.