IsaacChase

I've always known about these (being a native English speaker) but I didn't realize that's what they were called (unless you're making up a name haha). Also I think the trick is actually the word "take".

In, "I want to be clear, I didn't take the cookie", the reality of the situation was that maybe the cookie was given to him but he wasn't supposed to eat it. So technically he didn't "take" the cookie", the cookie was "given" to him.

Either way they're very tricky ways to sound honest. A really common one is:

Mom: "Why did you write on the wall yesterday?"

Son: "I didn't write on the wall yesterday.

The reality might have been that he wrote on the wall two days ago not yesterday. Little kids are really good at using "performatives".

Well a performative is a true statement that has nothing to do with the topic, followed by a lie about the topic. The true statement, "I want to be clear," qualifies the following statement, "I didn't take the cookie". 

Your examples are lies that are simply technically true. 

@Isaac

Yes, that is true. In German, if you say Ich bin heiss, it definitely means that you are horny :=), so you should say "Ich habe heiss".

It's good to know that's true, I've told that to so many people that I'd hate to find out now that it wasn't!

“In the first place, you’re way off when you start railing at things and people instead of at yourself. ”

― J.D. Salinger, Franny and Zooey

One of my all time favorite books. 

My first word, according to my mother, was "cookie".  But of course I pronounced it "ookie".

I hate to say this, but I think the F word is the English word with the most meanings.  It's definitely the word with the most diversity of uses. 

I remember my German professor talking about how in German, you don't say, "I am cold," or "I am hot."

In the German language, this refers to your sexual receptiveness, not your actual bodily temperature.  "I am hot," is like saying "I am horny."

What you say is "I have cold," or "I have hot".  Ich habe kalt. Ich habe heiße

Not having visited Germany myself, I have yet to try this out.

I also suggest to turn off the subtitles if it is a movie you've seen before.

This is definitely helpful and something that I do when I can.  It helps immensely if you already know the context when the words start flowing. 

I think the real problem is most people don't care. 

A lot of people have seen the demonstration of how spelling has little impact on the reader understanding the message.  It goes something like this:

"I cnduo't bvleiee taht I culod aulaclty uesdtannrd waht I was rdnaieg. Unisg the icndeblire pweor of the hmuan mnid, aocdcrnig to rseecrah at Cmabrigde Uinervtisy, it dseno't mttaer in waht oderr the lterets in a wrod are, the olny irpoamtnt tihng is taht the frsit and lsat ltteer be in the rhgit pclae. The rset can be a taotl mses and you can sitll raed it whoutit a pboerlm. Tihs is bucseae the huamn mnid deos not raed ervey ltteer by istlef, but the wrod as a wlohe. Aaznmig, huh? Yaeh and I awlyas tghhuot slelinpg was ipmorantt! See if yuor fdreins can raed tihs too."

The problem is that even though a lot of the stuff people type is readable, it makes the writer look like a fool.  But what is worse, there is a trend forming that people who take the time to write properly are being looked down as snobby, old fashioned or irrelevant.  I mean, even our President starts his weekly address on Youtube with "Hi everybody."  Not very presidential if you ask me.

A notable exception to this rule is the case if it's vs its.

It's is actually a contraction of it+is (as in "it's cold outside"). Its is possessive (as in "the dog wagged its tail").

This is one of many rules of our language that are fading from existence thanks to Facebook.

I've heard of this language trick lately and wondered what other people know about it.

A performative is when someone is telling a lie but they word it in a way that makes it technically true, which helps the fibber speak the lie with more sincerity and therefor makes it easier to believe.

An example: "I want to be clear, I didn't take the cookie."

The speaker is telling the truth, that they want to be clear.  This makes the lie easier to speak because there is a way that it can be viewed as truth.

What do you guys know about this?

I've been hearing about this more and more lately, how English speakers use a lot more sarcasm than many others.  I've heard lately that many European countries don't necessarily pick up on it, and it causes offense between people.  I don't have much experience with Europeans, other than a couple I met from Holland.  I'm a pretty sarcastic person and I didn't feel that that were barriers when we were talking. 

Anyone else?

Anything from Mr. Burns (Simpsons)

"What good is money if it can't inspire terror in your fellow man?"

That's great.

I always liked Vonnegut:

"True terror is to wake up one morning and discover that your high school class is running the country."

I definitely agree.  People seem to just throw words around without caring about whether or not they are the correct words or if they even are words in the first place.  This is how we get words like "hilarious" inserted into everyday conversation.  It's more than annoying.

I don't have any experience with online tutorials, at least not what the author is talking about.  But I can say that my son has had excellent results with using tutors over Skype.  I can't recall the name of the service we have used, but it connects you with a native speaker and you have conversations for set amounts of time during the week.  He was out of his immersion program for a year and it really helped him stay current with his Spanish.