Daniel Breslauer – If you can read Yiddish, why can’t you write it also? Try to get a hold of “Briefen Shteller”, a Yiddish primer of long ago.
Starwolf – Try reading any of the Apikorsim’s Yiddish stories or poetry; in addition to knowing the language, unless you are fluent in Tanach and minhagim and halacha of Shuchan Aruch that were practiced by everyone amalege tzeiten, you’re not going to understand anything.
Point is: You can’t speak this language without incorporating holy idioms and words connoting all aspects of Yiddishkeit.