Step 2: Dude, What's My IP?

Now you need to lay a breadcrumb trail so you can find your way in from points unknown. If your ISP provides a static IP (one that's always on and never changes), simply use that number in another Mac's Connect To Server dialog (in the Finder, select Go > Connect To Server) to log in. If your account provides a dynamic, changing IP, you'll have to note your current IP address and hope you don't lose the connection. Either way, in System Preferences, click Energy Saver, and then click the Options tab. Check the Wake For Ethernet Network Administrator Access and Restart Automatically After A Power Failure boxes. Then, go to System Preferences > Network, select Network Status from the Show pull-down menu, and jot down the reported IP address.

You can't access your Mac if it's shut down. (Duh...)