NYCLEX gives some great tips and he makes me laugh with a good point -- it is incredibly difficult to know what you want to do in high school! Part of the difficulty is that the job is usually not what it seems to be or what you've been told. In fact, the big joke about law school is that attorneys learn nothing about being a lawyer in law school... and there is some truth to that!!
The best way to have an understanding of what it is you may want to do is ask people to let you assist them, even if it is free. What you will get is knowledge and that can be priceless. Don't think of some of this as free labor, unless they aren't giving you a return on investment. Some attorneys will like your bravado and honesty and will be charmed by it and take you under their wing. You can find time to ask questions about the different law they practice(d) and their experience. You'll get a feel for what being a lawyer is REALLY all about.
NYCLEX made some great points about the fact that not all lawyers are in court. Many never make it there. I like to divide up the different specialties as follows:
1) Criminal Law: This is very different than civil and you will very likely be in court. There is also usually a type of personality that will enjoy being in this area and you'll get a feel for prosecutors, the personality and what makes some very effective and others not as enthusiastic. You'll probably know whether this is for you or not pretty quickly -- especially when you see the pressure and ridiculous number of cases prosecutors are asked to handle. Given the salary this is usually an indication of a true desire to "donate" part of your time for the greater good. On the flip side, being a criminal defense attorney also has characteristics and decide whether you feel comfortable with the thought that you may be asked to defend someone who is truly guilty and whether you can stomach that thought.
2) Civil Law: This is the area of law which is not dealing with criminal law and there are many flavors. You can be a courtroom lawyer and deal with general litigation. This will typically involve a lot of preparation although some live for the courtroom experience. Others love to write great briefs and be the strategists on paper. If you want to stay away from the courtroom there are various types of business law that you could pursue: Licensing of Intellectual Property (e.g. articles in magazines, books, music, anything copyrightten, licensing of company trademarks), general contracts (e.g. in-house counsel for a company negotiating deals from real estate to widget sales and purchases of raw materials), wills, trusts and estates work, tax law (dealing with taxes of a corporation or high net worth individuals), insurance law...
As you can see, there are many areas of law just like in medicine there are so many disciplines. There are surgeons and some who never ever get close to the operating room such as a primary care physician.
The best way to figure out what you might want to do is by seeing it yourself. Be around the people who perform what you think might turn on your creative juices. Share your thoughts with us and we'll be glad to share our experiences with you.
Good luck!!