I have to rebuild a website. The website has a custom build CMS and this CMS has different modules. All modules should be taken to a Sitecore project since the website has to be rebuild in this CMS. I am finding it hard to write a good Technical Design document for a project in Sitecore. This is because this is the first project that I will work out in a Technical doc for Sitecore. I hope there are people around that already done something like this for a Sitecore Project.
What are the best practices for setting up Technical Design doc's for a Sitecore project? Would you just design all different Data-Templates and then be done? Write down any experiences you have with the setup of a Sitecore project from scratch.