I second going to the Port Wine Institute. Four of us ordered a glass each (two white, two red), and passed them around the table for tasting. I thought the 10-year-old ruby port was smooth until I tasted the 20-year-old one! We ate at a traditional restaurant along the waterfront one meal, and at a simple pizza place near the Institute. Be sure to take the tram up to Castelo Sao Jorge for a beautiful view of the city and the Tagus river below.