I would add to this that Jamis Buck, who created Capistrano, also created a gem specifically for setting up multi-stage environments with Capistrano. You can do it without the gem, but the gem makes it even easier. You can find his post on it with instructions here: http://weblog.jamisbuck.org/2007/7/23/capistrano-multistage
There's also a very helpful article in the Pragmatic Programmer book "Advanced Rails Recipes" that walks you through exactly how to set this up. I found that the answers to this post, combined with the Rails Recipes book made this incredibly easy to set up.
StackOverflow won't let me add another link, but if you google Advanced Rails Recipes, the book is the first result.
