I assume you are going through paypal? If not and you accept money orders as well, then send him a message with an invoice attached (you can do this through your listing) and say you will put it up for listing again if you do not recieve payment in x number of days. After that point has passed and you have recieved no money, alert Ebay and give negative feedback.
That is the professional way to do it. Trust me, I've sold over $4000 worth of goods (guitars and guitar pedals) through Ebay, and this is the way to do it.