First off, taking tax advice from an internet forum is just about as smart as taking legal advice from an internet forum, which is to say NOT SMART AT ALL!!! Whatever anyone here tells you, you need to take the time and do the research to verify for yourself.
Having said that, the short answer to your question is, no, you do not get any special tax break for being 18. You still have to file a return and pay, or not pay, based on what you earned during the year. There will also be some differences depending on whether or not your parents claim you as a dependent. In particular, if your parents claim you as a dependent then you cannot, on your own return, claim a personal exemption for yourself; this rule will probably increase your taxes while reducing your parent's (who are probably in a much higher tax bracket than you).
Bottom line is that you should be working out your own taxes in coordination with your parents, at least if you are still dependent on them. If you have been living completely on your own and were NOT a dependent of your parents last year then you should probably buy Turbo Tax or Tax Cut and go through the steps in it to calculate your taxes. Both of these products work pretty well, step you through the process, and have good tutorials and links to explain the tax laws to you.
Good luck!