Capacity Planning - Series Start

I was asked by my department to take a session on how to do the capacity planning process for a database infrastructure. Since, the community includes data services professionals across a lot of platforms and communities, I tried to make the session a very generic one. I will be writing a series of posts to cover what all I presented in the session. I know there will be a few instances where things would be explaned with the help of SQL Server (as that is by far my expertise); forgive me for that :-)