Berlinerisch, also referred to as Berlinering or Berlinisch, is pretty much what it sounds like: the dialect of German spoken by Berliners. Any native German can tell a Berliner just by how he talks, including differences in accent, slang, and even grammar.
A Note on German Dialects
German has numerous dialects with substantial differences between them. Many linguists even argue that since many of them aren't strictly mutually intelligible that they should be classified as different languages! Many are still commonly spoken in their respective regions, within and without Germany itself.
So, what do we use to compare Berlinerisch to? During the last century, especially with the rise of mass media and educational standards, a homogenized dialect has emerged: Hochdeutsch. This has since emerged to be the standard German that students learn in accent, grammar, and vocabulary. This is the dialect that Berlinerisch will be compared to for purposes of this article.
Also, keep in mind that languages and dialects are a fluid thing: Your experience with Berlinerisch will vary by the individuals you talk to, the parts of Berlin you wander in, the movies you watch... there is no canonical version of Berlinerisch, or indeed, any language (l'Académie française aside).
Berliner Accent and Pronunciation
What is the most conspicuous difference in accent between Hochdetusch and Berlinerisch? The famous “ick bin Berliner!" At least in Hochdeutsch, the convention is to say “ich", with the “ch" sound coming from the back of the throat, as if with a bit of a cough. Berliners, on the other hand, say it with a harder “ck" sound, just like in English words with a hard “k" sound.
Another example is the tendency for Berliners to replace the final “s" in many common words. For instance, “das" is often just pronounced as “dit", “was" like “wat", etc. Changes like these beg where the line runs between a funny pronunciation and whole new words, of course.
Many words ending with “er" also tend to lose that, turning more into an “a" sound. Think “Wassa" instead of “Wasser." The “r" sound tends to get dropped elsewhere as well, especially when they're speaking fast.
Many Berliners also tend to pronounce hard “g" sounds as soft “j" sounds at the beginning of the word. For example, “gibt" is often pronounced “jibt" or “gehen" as “jehen."
As for examples of specific changes, “auf" is often pronounced more like “uff" and “einmal" like “eenmal."
Berlin, ich liebe dir! Look weird? It should: in Hochdeutsch, one says “ich liebe dich." The difference is that Berliners use the indirect object instead of the direct object for many verbs, the dative case instead of the accusative. There's no real difference in meaning; just a Berlinerisch quirk.
Another important difference is that many Berliners tend to use the dative case instead of the genitive case, both when denoting ownership and for prepositions and other constructions that normally require the genitive. For example, “Wegen dieses Freundes" becomes “Wegen diesem Freund", and taking into consideration pronunciation differences, into “Weg'n dies'm Freund."
Just like in English, slang is very sensitive to the era in which you live and the social groups in with which you interact. You won't catch too many Portlander hipsters of 2009 saying “groovy," for instance. So, bear in mind that slang is a volatile thing in a language, and without living there, there's no way to keep up on the changing nuances.
Some examples: a dumpling is usually referred to as “Klops," and the verb “schauen" (to look) is replaced with “kieken."
There are also many slangy terms that Berliners will use to refer to locations within their own city, names you won't be finding on any map. For example, the “Alexanderplatz" is often referred to as just “Alex."
As you might expect from a major metropolis in the heart of Europe, there have been many influences by other languages on Berlinerisch slang and vocabulary. A great example of this is the role of French in Berlinerisch, originating from the immigration of the French Huguenots: “seefe", derived from the French phrase “c'est fait", which means “it works," and similarly, “Maller" is derived from “malheur", and “pö à pö" from “peu à peu."
Of course, there are many more words and ways in which Berlinerisch differs from Hochdeutsch than is mentioned this article: no single resource could ever possible teach all the nuances of this dialect. Here are some more resources to help you along: