There are some configuration concepts for Sitecore that require some planning.  This is especially true for larger environments.

Below are parts of the planning document we created for a recent client.  The site being considered here is characterized by the following: staged environments (development, QA, production), multiple content delivery servers in QA and production, a large content authoring team, all running Sitecore 6.1.

An early version of this plan was discussed with a contact in Sitecore USA.  His feedback has been applied to this document.  Sitecore was very helpful, even providing code samples for some of our needs.