Here is my reccomendation. Keep your head down, keep a low profile. avoid the authorities as in dont run away from them, but like avoid gettin involved with them. Dont get involved in anything illegal (obviosly).
and the biggest rule of all.
ALWAYS assume that you are surrounded by insane paranoid freaks who will suspect terrorism at a drop of a hat. Trust me there is always some crazy paranoid freak especially in the states who can suspect something suspicios out of something stupid. Thus make sure that most of all you protect yourself from crazy people like that. For example, in the airports, dont stuff your pockets with stuff that it takes you really long to empetey out and just prepare in a way so you can get trough security quickly. (this will also save you a lot of time and hassle) avoid carrying self made electronic devices (like i have an MP3 player in a custom metal case that some people might think is some remote bomb device) also generally avoid carrying too muych electronics as they always ask you to take out your laptop and scan it seperatley)
always make sure you can quickly get out your ID if you are stopped for an ID check (not that it might look suspicios, that you take too long to find your passport, but cops might get annoyed by it or maybe the cop is having a bad day and they night do something. Always be polite to authority figures and answer questions honestley and straight forward. and dont make any jokes about terrorists (i made that mistake before)
I mentioned airports because, it has tons of security, and i suspect a large concentration of paranoid people as well as paranoid staff. Also it seemes to be the most paranoid place ive ever went trough, and sometimes had problems because of stuff (luckily no serious consequences) Other than that, you should be fine as i lived in the states myself for a long time and i figure that its easy avoid any troble with opressive law enforcement. You just have to be smart and avoid doing stupid stuff. (i did stupid stuff so dont be like me)
Also, when you are in school and at work or anywhere outside of close cirle of friends/family who you know you can trust, Avoid speaking out your political views or opinions about OWS movement or corporations. Because again there are people who can turn that against you. Your boss might fire you, and depending on who is listening, your political/social views could end up in your profile at the FBI headquarters and if you get caught for anything, these guys can use anything against you, even if you are a freedom-loving hardworking patriotic citizen, these days might sound like "extremist/ nationalist"
Again, at one time i spoke out my support for Michel Moore in school once (before i lost respect for him) my teacher got insanley angry with me and just started throwing all kinds socialist hating BS at me and even tho he was totally wrong and i could prove it, i decided that the smart thing would be to just shut up because this guy is one of the oldes, most respected, educated and influential figure in the school and not only. He also participates in some other orgonisation being a financial advisor or something like that IDK.
The key thing to know about such a system is that they make laws on purpose that anyone can be arrested under any pretext if they need to. They arent going to toch you if they have no reason to. If some people decide that you may know too much about something or if you are a thorn at someones side, they can get you arrested easily. Thats because you are proboly already a criminal. The FBI and national scurity, proboly has an entire list of crimes you committed for which you can get arrested. Hell I am also a criminal, I proboly have a file in the criminal database at the FSB archives somewhere. So just dont give anyone any reason to arrest you.
I live in russia and compared to america its a much harder place to avoid the authorities than in america because the cops in moscow are very dense'ley (?) spread out. and i am required to carry my ID all the time and if i dont have mine, they have the right to detain me. I even avoid drinking soda in subway stations because cops often stop me and check to make sure i am not drinking alcohol. And i am in a tight situation. I am dodging army draft (they cant take me in legally since i never signed a slip, but they can put a lot of pressure on me if they want) And Moscow sufferes a lot more from terrorism than all of america so they actually have a reason for tight security here.
Also, protecting yourself on the internet is also important. there is a very small chance that they are actually reading trough your emails (unless you are a jornalist or some activist) but you can never be too careful. for that you might want to read about "TOR networking" if you want to stay off the radar (plus immunity from protect/IP law)
Anyway, i am seriosly sorry for whats going on in the States I lived 10 years there and have lots of friends left there. And i dont hate the country, like most because i dont see only the bad, i also see many good things about the states.
so just try to follow my advice and you should be fine.
[EDIT] BTW what state do you live in?

dont hate people who rip you off,cheat and get away with it, learn from them