Personally, what I did was buy the Mass Maritime books, and Mariner advancement software. Read through all of the questions in the books, used the software to study the illustrations and take notes in the MMA illustration book. The software was also useful in seeing where you are at by taking practice exams, though Seasources.net is free and could be used for that same purpose, but it does require an internet connection. I made sure I got around a 90 on my practice exams, which might be a bit too high. Most people say 80-85% is sufficient.