Best practice for deployments and multiple environments?

I have been developing Pseudo Exchange for some time now, and I want to manage things right on it.

I just signed up for Bean Stalk and was fartin around on it and I figured out how to successfully deploy a repo onto a server.

My question is this...

I want to set up a development subdomain (dev.pseudoexchange.com), but I am not quite sure I'd know how to set everything up properly. I don't want to reinvent the wheel here, so let me tell you what I think the process is, and you tell me how I am wrong! :D

Set up the subdomain dev, and a seperate dev branch in my git repo. I deploy the files to the dev from the dev branch, yada yada testing testing, but what do I do when I want to make those changes live? Do I deploy the dev git to the live server or is there a different way of doing things?

Jacob