There are a lot of different types of self study Spanish language courses out there, which include a lot of different methods of trying to help people learn Spanish. Different courses go about teaching in different manners. Sometimes this is due to the purpose of the course. A business Spanish course may focus on commonly used business phrases and words and have a lot of business type conversations.
One of the methods used to help people to learn Spanish is to teach them useful phrases as mentioned above. A course geared toward travelers would teach them the most likely things that would need to be able to say while traveling. These courses do not really focus much on grammar, just useful sentences, phrases and vocabulary; This method is mainly meant for people who want to pick up a few basics and do not have time for a longer course.
Another method for helping people to learn Spanish is more like that used by schools. They focus on teaching grammar and vocabulary, and use sample conversations as examples for the grammar lessons. It can take a longer time to build up the vocabulary necessary for business or traveling this way, but it does give you a stronger base and you will be able to say a lot more with the proper gram under your belt.
One of the newer methods focuses on teaching different words through a computer program and shows you different combinations of written words, pictures, and spoken words, asking you to match up the ones that go together and working to quickly build up a vocabulary. Once a certain number of words have been taught, they start to use phrases and then sentences. This method will take the longest to actually teach you useful conversational sentences, but it builds up a great vocabulary base and you learn a lot very quickly.
The program you choose to help you learn Spanish will depend on your ultimate goals and which method will work the best with your learning style. Private lessons with a tutor or immersion programs would probably be the fastest way to learn what you need to know, but many people need to rely on these self study courses due to the cost of these other methods or time constraints that do not leave a lot of time for language study. A motivated person can learn a language with a self study course, though it will take time.