There are sub-specialties, but you do not study them in law school the way you might in medical school. There will be offerings of classes in various areas, such as IP, that you can take, but your best bet is to try to get a job during the summers with a firm that practices in the area in which you desire to practice, and will allow you to work in that area.
If you want to be a patent lawyer (which is always a good area) you need to have the correct undergraduate degree. If you want to focus on other areas, for example Tax, go ahead and take the few courses in school that you can, but you will also might want to get an LLM (additional degree) in that area.