Once you have the layouts, you need to write out descriptions for every interface element on each page. This is simple in itself once the layouts are produced. The harder part will be organizing the written specs in a concise non-repetitive format. Generally, the idea is to build a spreadsheet of tasks for each page. Each task is description of one feature of the product, i.e. of one user interface element.
Some times you’ll have features that exist on multiple pages, and you may end up describing the feature in the written specs associated with 2 pages. That’s fine, but in each place reference the other places. Also have a list of global overarching tasks. If there are things that are similar from page to page--for example how your forms should operate--make a spreadsheet that lists those tasks. If you have a header or sidebar that is always present, give them a sheet of tasks. After that, you should have a list of tasks specific to each page.
The next thing you do is use your project management software to create groups of tasks for these sheets. So that means each page has its own set of tasks listed in your project management software. Then you have your global groups. All this should be very product-centric, i.e. describing user experience, rather than deep technical notes. Though, in my opinion, don’t be too strict with yourself. I you are technical, and have some technical notes to add, add them. However later, your tech team will add deeper technical tasks as sub-tasks. Therefore you need to be using project management software that allows deep nesting of sub-tasks. We use FogBugz, which we’ll cover in the next tutorial.