New businesses have a greater challenge - they will rely more on market research using libraries, trade associations, government statistics, surveys, competitor observations, etc. In all cases, make sure your market analysis is relevant to establishing the viability of your new business and the reasonableness of the sales forecast.
As importantly, it also identifies road blocks - in advance. Your business plan should provide a common vision supported by tactical initiatives that, ultimately, creates greater value for your company. It may seem daunting, but by knowing your vision and its corresponding financial targets, you will have a better chance at executing how to get there and avoiding traps in advance.