If your laptop is always on and using wired connection then simply choose the Ethernet IP to forward an open port on the router. This would be the better selection to choose from.
For the ports I always choose something non standard and not the registered port. So, if I'm running SSH (default port 22 on server) I would open 2222 on the router and forward that as port 22 to the server. Or with FTP service as 2121 on router to 21 on server or whatever you wish. Doing so cuts down automated target attacks. Just make sure you also have other firewall or white lists in place.
You could also use a service like gotomypc or logmein and install the client on the laptop avoiding the forwarding ports part.