When working on large websites, I often work as a gardener rather than an architect (see Architects and gardeners).
We start the process by sowing seeds and nurture them into the pruning stage. We then usually hand the site over to the new caretakers – the client, who will hopefully continue feeding and pruning the website.
Pruning and updating the content the website is just as, if not more important than creating new content.
A fairly involved pruning approach could be content auditing.