Business to Business Web Driven Database

Hello Ladies and Gentlemen,
I am a graduate student tasked with developing a plan for a "Business to Business Web Driven Database". The assignement is a comprehensive database plan to allow a Manufacturing company to order materials from its vendors via the Web.

What I am searching for is a database plan template or any other tools that will walk me through a successful plan, not leaving out anything important. Just in case you are wondering, this is going above and beyond the requirements for the class, so I am not looking to cheat, only, to use real world tools.

Thanks in advance for your advice and direction.