More important, however, is reading insider reports and narratives. This include reading their core newspapers (they don't have TV, Internet or radio) and magazines. An education in Yiddish and secondarily Hebrew would be beneficial. Yiddish is their prime language; they believe it to be the only and true 'Jewish' language and even though many may grow up in America, many of their children may never know or speak English.

A knowledge of Hebrew and Yiddish would be invaluable to reading their texts and absorbing oneself in their culture.

Attending their schools, and preferably enrolling in their schools for at least a year, would be helpful too. Doing this, would involve one in their milieu and have them participate with their teachers and students gaining an unprecedented perspective of their thinking and way of life.

A visit to their homes on Saturday and/or Festivals is also illuminating but far less so than if one were to, somehow or other, get...

An outsider would be almost invariably recognized as such and treated in a detached, distant manner. Respect (although not always) may be there, but the investigator will forever be excluded from authentic data.
On the other hand, an insider -even one who seems to be slipping or who has already slipped -- will always be acknowledged as part of the group and, therefore, privy to 'insider' information.

My recommendation, in short, therefore, is to study the behavior of the group form movies and material written by 'outsiders'; to incrementally gain the 'insider perspective' aggregated from 'insiders', and to penetrate the group -- slip into it / melt into it -- as an 'insider'. It is in this way that one gains the most authentic data.