Yiddish
Status: Official Style Guideline
Hebrew Script (In English)
Hebrew has no capitalization, so this isn’t an issue.
Latin Script (In English)
The first letter of the first word and the first letter of any proper nouns should be capitalized.
All other letters should be lowercase.
Examples
“Yismakh Moyshe / Yismekhu” (note that Moyshe is a name)