If you know the SURNAME
Begin your search with a basic query
JewishGen/Family Search: query with the first and last names could yield census records (birth/death/parents/spouse, etc.)
Yad Vashem: query with the first and last names could yield entire family lists, evacuation address, professions, family's address during evacuation
Russian site 'Pamiat Naroda': query with surname and/or town, the search might yield names and military service details, including place of birth, pre-war residency, last known address, address of relatives (including evacuation address)
If you only know the TOPONYM
Begin your search with a basic query
JewishGen/Family Search: the toponym query will return {long} list of surnames
Yad Vashem: geographical query could yield family lists, evacuation address, professions
Ukrainian/Belorussian Geographical Dictionary could help narrow down the search
Geographical Dictionary of Polish Towns : a query with a town/hamlet names would yield historical-demographical details ( population, settlement time, land owners names, etc.)
If you only know a GENERAL AREA
DO NOT despair - use your name & surname
If it is a toponym - see subclause #2 above
If your surname is NOT a toponym - look for your surname distribution in the region of interest
You will still learn a lot about your Jewish ancestors
Refer to 'Basic Words Dictionary' : Russian , Ukrainian and Polish
Use Google translate to convert your surname into 'slavic' or 'ashkenasic' format
Old Church Slavonic - Old Russian alphabet