Sure there's an apostrophe in German – see §§ 96 and 97 of the official ortography rules [1] and the explanations at [2], for instance.

[1] http://www.duden.de/sites/default/files/downloads/amtliche_Regelungen.pdf ;

[2] http://www.duden.de/sprachwissen/rechtschreibregeln/apostroph

I also have never heard this before.

There are rules when to set an apostrophe in German - listed in the "Duden" (DonHolgo has already given the link)

As far as "Wie geht´s dir" goes:
Rule 14/4 (Duden) states:
"Bei umgangssprachlichen Verbindungen eines Verbs oder einer Konjunktion mit dem Pronomen „es" ist der Apostroph entbehrlich; er wird jedoch häufig verwendet. ---Wie gehts (auch: geht's) dir?"

@Ghatol Bawari: Could you give us more information about the rule that "Wie geht´s" is the "biggest mistake"?

I've never heard this before.

I'm aware that that there's no apostrophe for the genitive form of names ( 'Peters Buch', for example).  But otherwise, all the German grammar books that I've ever seen teach students to use apostrophes in much the same way as they are used in English - to show that something is missing.

For example, isn't  " Wie geht's dir?" a contracted form of 'Wie geht es dir?'.  The apostrophe is showing that the subject 'es' is abbreviated. 'Wie gehts dir' looks confusing to me - I wouldn't know what the subject is, or who or what the verb form 'gehts' refers to.

I'd be interested to hear whether other native German speakers agree with the idea that their language has no apostrophe. If they do, then we've been learning something wrong all these years!

@DonHolgo wenn es schwer verständlich ist oder es missverstanden werden kann.

Ich habe zwei Seminare zu diesem Thema besucht und im Falle " Wie gehts dir " darf es nicht verwendet werden.