you can set up the skype options to show when you are online and when others come online. my family and friends are over a few countries and continents. we use skype all the time and all have each other linked as contacts, when one of us comes online we can see because their status is shown in skype, and a little window appears to show when they come online.

as has been said, you need to have it on each computer before you leave, and you need to send a contact request from one to the other to establish the link. you can do this in the same room before you leave, so that you can see what will happen if a call is made/received at each end.

always useful to have a practice - pictures paint a thousand words!!
also you can use skype to pass documents and files. in the box where you type comments, you can drag and drop a file and it will be passed between the contacts. i find this useful for documents that are above email limits for file size. you can drag and drop big photos etc!!