Do I need to sit for TOEFL or SAT? I'm actually an United States citizen who has been living and being educated in Malaysia.  So currently my family decided to send me back to the States to continue my future studies.  Some people told me that I need TOEFL/SAT results to prove my English but some of them said that I don't need it because I'm a citizen.  I'm kinda lost now...
What should I do to prepare myself before going there?
As Nate Eldredge already mentions in a comment, there will be a statement somewhere on the application page that specifies who needs to provide language scores as part of their application and who doesn't. Since schools receive large numbers of applications, there isn't really any leeway for special cases: Just follow the letter of the application requirements. If this requires that you to take the TOEFL or SAT, then that's what it is -- whether you think that's fair or necessary or required is a question that's entirely unimportant.