The best place to find web templates is to search on the Internet. There are many sites to search templates and they frequently provide good supplementary details and technical support. You can regularly see a sample of the template you are taking into consideration.
Are there emerging markets or market segments? Where does this product or service currently perform best? Possible Data Sources: trade associations; trade journals; attorneys & accountants dealing with the industry; industry salespeople; state business websites; focus groups.
But your idea may be so new that you may also need to talk to potential customers, host some focus groups, talk to an ad agency, or maybe even make a prototype and float it past some people. Be prepared to spend the time. Remember, it's not about the Plan but the Planning.
However, the best business plan template is that which meets all your business needs and requirements by offering you a high level of customization and a professional layout of all the content that you would like to include.