Where in Williamsburg is the Hasidic/Jewish section?
Specifically, by train, where should I get off, where should i walk?

It's in Southside Williamsburg, just south of the Bridge.

(J), (M), or (Z) to Marcy Avenue. Walk south past Broadway and you're there.

There are no Hasidic shops or restaurants for tourists in this area, if you are not a member of this community you will probably be stared at or made to feel unwelcome. Very few Jews live in the area that are not a member of the various ultra-Orthodox Hasidic communities, it will not be a fun or 'ethnic' experience for out-of-town Jewish visitors.

All stores and restaurants will be closed on Friday night and all day Saturday. Reading or speaking Yiddish will help a great deal if you want to do business. Unescorted women will not be welcome in some stores.

I strongly advise against stopping by just to take photos or gawk at Hasids.

There are many fine shops and restaurants in Southside Williamsburg - none cater to the Hasidic community.

If you are looking for the "getting in touch with my roots" experience, stick to the Lower East Side. If you would like to experience a modern Orthodox Jewish neighborhood, I would suggest visiting Borough Park or Midwood instead - (D) to Ft. Hamilton Parkway [Borough Pk] or (F) to Kings Highway [Midwood].

I wholeheartedly agree.
Boro Park will welcome you with open arms - the shops are open - you can watch the women have their wigs set, buy kosher food and see seamstresses sew long skirts.

The Chasid community is kinda being pushed out by the new hip element of Williamsburg. But if you want to see great art and eat fab food, head there anyway...

When I ran through Williamsburg during the NYC Marathon, it was really interesting to see.

My husband, who was with one of my girlfriends who is Jewish, said no one would speak to them until my girlfriend asked one of the women a question in Hebrew.

Thank you all. I will check out both. I really just want to see the area in Willamsburg, not be a gawker or a consumer.
Thanks, again

If you go to Midwood, you can visit one of the best pizza places in the city: DiFara, on Avenue J at 15th Street. Truly one of the great NYC experiences.