Give me your American slang!

I know that the American nickname for McDonalds is Mickey D's (in Australia we call it Maccas )

And I love the y'all abbreviation as well!!

Another filler to go along with "like" is "y'know?" or "y'know what I mean?" Probably those are used everywhere, but Americans definitely use them a ton.

I think that you might just want to leave slang out if it doesnt come naturally to you. It might sound kinda off no matter how hard you try. I could be wrong, though.
And like the rest of the guys have said - Where in America is a big deal. Like, I'm from the south and yes, I totally use the stereotypical "ain't" and "Y'all or Y'uns". And then there's always the stupid sayings that the south has like "Look at him - runnin' 'round like a chicken with its head cut off." Gruesome, yeah, but I hear it all the time when someone's running around with any real purpose.
But other slang I hear...
"Aw, man." or "Aw, dude!" are basic exclamations that I hear for just about any situation.
"See ya, later" or just "Later" for goodbyes.
My friends and I use "Seriously?!" a lot when we're shocked.
If you want anything more than stuff like that, then I'm afraid you have to wade into the world of insults and curse words. I think we cuss, alot.
I hoped this helped some.

Well, I know where I am at the moment we say things like this:

Jenk - Awesome
Woot - Sweet!
Pwned - You lost.
N00b - Idiot or imbecile.

Depending on which part of America you're in, you'll hear different kinds of slang. The southern dialect has been explained, but Californians also have their own way of speaking. Instead of saying "hell of" we usually just say "hella." "Like, oh my god" is also part of the valley girl speech, which was named after the denizens of the Sacramento and Central Valley. We also tend to speak faster than the rest of the country.

Reckon is a big one. It's sort of a country way of saying "think."

"What do you reckon, think we should take a look?"

"I reckon so."

A weird place to go is West Virginia. Deep in the Appalachians, people will occasionally speak old English. Instead of help, they'll say holp. Instead of saying they don't approve of something; they'll say they don't hold with it. For example

"I don't hold with it, but I holped him anyway."

To add in some more input, I'm from the Southwest, Four Corners area. We pick up a little of the Californian dialect and mash it up with the Texan one haha. A few people say y'all and and we slur our words together, but we lack the stereotypical drawl and speak quickly. I'll parrot others in saying that where your characters are from will greatly affect their slang.

Epic, win, and fail are common due to the internet and all. Actually, a lot of internet terms are used, so if you're familiar with those, that might help. My friends really like a certain kind of slang that revolves around drug culture...don't ask why, they're just weird. -__-

From the people I know, I hear things like

"legit" - short for legitimate, typically used as "That was legit!" It pretty much means that something was legitimately cool, or scary, or whatever rather than...something that wasn't legit xD A recent example I can come up with was that my friend couldn't ride the rides at Disneyland because of an Earthquake. Someone replied, "Well, that's legit." As in, legitimately scary.

"sketch/sketchy" - this is big around here right now. It just means that something or someone is suspicious, shady. You know, like you don't have the full picture, just this sketch. E.g: "Dude, that alley is so sketch. I thought I heard someone scream!"

Words to show general approval include: sick, dirty, sweet, awesome, cool, dank (I personally don't approve of this one), choice, dope, beast, fierce (this one's big).

And slang usually just stems from pop culture! I know Tyra Banks helped popularize 'fierce'. And Donald Trump with "You're fired!" Just watch some American films and that should help as well

But you might want to look into American dynamics in terms of conversation! I don't know how different it is from other cultures besides the one I know, but I've noticed that my Asian part of the family doesn't quite get my sarcasm in the same way my American friends do. Like, I say "Just kidding" when I make a mistake, and my mom thinks that I broke the plates as a joke! It's all rather interesting.

Good luck! And if it happens to be a little awkward, well, that's what YWS is here for!

We say wicked a lot where I'm from. Like, "That's wicked cool." There's also the occasional "stellar" which can be another word for cool.

Well , on the east coast, specifically in massachusetts we say :
Salted- pretty much is wen you get disssed - as in you get insulted someone will say " you just got salted" or just "salted.!"
Yo- can be used as a greeting or anyway pretty much
Oh my god- no need to define it
your dry- this is used wen a joke or something you say is meant to be funny but it makes absolutely NO ONE laugh someone would go "shut up, your so dry." (we're pretty harsh where im from)
thats dope- thats cool
chill- calm down
going out with mad heads- going out with alot of people
thats all i've got hope i helped

I'm from Central PA, and a lot of our slang is peppered with Slavic words. Like, we say pumika, instead of dishcloth, and dreshlak instead of colander. (my transliterations of the Slavic words might be wrong, but you get the idea.)

It also depends what time period you're in. my parents, and a lot of their friends say goofy stuff like groovy.

Hmm... stuff like:

Crap, Geez, tight, sick, smooth

Aha I can't think of much more right now XD My novel is screaming at me. Hope that helps!

Or... (I don't know if this has been said yet)

Man, that was ill!

Flip is another word. Like "Oh, flip!"

I'm American. Here in New England we say "Wicked" for like awesome and cool.

"That's sick!" Also means awesome.

"Crap" or "Holy Crap" when you stub your toe.

"Oh my God" is a common one.

"Whatever" means I don't care.

Oh and new things like "Fail" "Win" "Epic" "Awk" or "Awkward" I think those are self explanitory.

"What's up?" Like whats going on.

"Legit"

The single most important American slang word you need to know is "Awesome."

In fact, "awesome" is so integrated into American English that look, everyone before me was talking about it as if it weren't slang at all. You'll hear anyone up to the age of maybe 60 or 70 use it by its slang definition.

As others have said before me, though, a lot of the slang is regional, as are other aspects of American English and all its dialects. While you can't go wrong with 'awesome' and you can never go wrong with 'cool' (that word's been a part of American culture for at least half a century) to describe things that are.... impressive or eye-catching or in-style or agreeable, other slang is a lot less universal. The words we use for soft drinks, for instance: http://mappery.com/Pop-vs-Soda-US-Map

In addition to where your teenagers are from, it'll also depend on who your teenagers are socially. While everyone around here, being Internet-savvy and such, will probably use 'epic' and 'win' and 'fail' and 'epic fail', you probably won't hear the same from teens whose Internet and computer know-how is limited to Facebook and Myspace, especially if they don't hang around "computer nerds" and have a disdain for them.

But, in the end, you're always safe with "What's up?" for a familiar greeting with someone, and "awesome" and "cool" are nice and generic but still American. Oh, and we can't forget "That sucks" as in "That's awful/I'm sorry/expression of sympathy or empathy" and "This sucks" as in "I hate this situation I'm in, won't you please commiserate with my poor self?"

Ah, American slang. Admittedly, I use it everyday.

The Mizz's List of American Slang:
Dude - guy
Awesome - ...um, awesome?
Freakin' - um, a version of a certain four letter word
Like - okay, so this isn't exactly American slang, but a lot of people insert "like" a lot in there sentence. For example: That was, like, so totally cool, like, oh my gosh!"
Dat - that

Hmm, well that is all I can think of right now. Hope this helped.

-Mizz

Yeah, just to reiterate -- American slang is super spotty and super regional. More than half of the stuff listed in this thread is completely foreign to me.

The only -truly- universal American slang word, in my opinion, is "cool," which has somehow survived generations of linguistic recycling. "Awesome" was kinda 90s, but definitely still gets some usage.

It's also true that almost everything Americans say, even non-Valley Girls, is peppered with at least a few "likes" and the occasional "y'know." A "like" can function as a filler word like "um" in some regions. If I record myself conversationally talking and replay it (which I did once for a creative writing class...) I barely get through a sentence without a "like." However, I wouldn't dare write a character who used it with the frequency that I do in real life. It's another deal where you have to temper realism with what works in fiction.

I also hear a lot of "epic" and "legit." Anyone else here hear "totes" as a shortened form of totally? As in, "I am totes sick of this report" or "that was totes awesome."

Honestly, you could probably get away with writing American teens without using American slang, if you managed to stay away from colloquialisms from other regions. But I'm sure anyone here will be glad to help you out if it's still a bit awkward when you post it.