Choose a map large enough for the cruise that you want to plot out. It is a good idea to get a basic map without a lot of identifying marks on it, so that your own identifiers do not get lost. A world map is a great idea, if you go on a lot of cruises or even on a world cruise. If you go on cruises in different areas, obtain maps of those areas and separate them. You can include many cruises on one map, or designate just one cruise per map. If you would like, you can even use a globe.
Creating a legend is especially important if you are going to plot out more than one cruise on a map. Designate a specific color for each cruise line, and a different shaped line for each cruise itinerary. Be certain to clearly write out the legend on the map so that people can decipher it.
Using information and smaller maps from the newsletters delivered to your cabin on the cruise, plot out the location and the course of each cruise. Use the color designated for that cruise itinerary and cruise line.