It is not common for a Reform congregation to respond to blessings. Beth El, however, follows this tradition at the Saturday morning service.
There is no clue in the prayerbook revealing when or what to respond. One just has to know. This section reveals everything one needs to know to properly respond to blessings at services. It is really all quite simple.
All blessings begin with the words
Baruch Attah Adonai
[Blessed are You, God]. According to tradition, upon hearing another person start a blessing by reciting these three words, one immediately responds
Baruch Hu, U'Varuch Shemo
[Blessed be He, and blessed be His name]. Once the person completes the blessing, one then immediately says
Amen
[It is true].
This tradition is (partially) followed at Beth El during the Saturday morning service. The Cantor (or whoever is leading) will pause briefly after saying
Baruch Attah Adonai
to permit the congregation to respond
Baruch Hu, U'Varuch Shemo
. After the Cantor finishes the blessing, the congregation will respond
Amen
. The Cantor will not say
Baruch Hu, U'Varuch Shemo
or
Amen
himself; according to tradition it is inappropriate for a person to respond to his own blessing.
Although according to tradition it is ``proper'' to respond to almost all the blessings recited by the Cantor or leader at a service, at Beth El typically the only blessings the congregation responds to are the blessings recited after the Haftarah reading at the Saturday morning service.
For the sake of completeness, these are the blessings it is inappropriate to respond to with
Baruch Hu, U'Varuch Shemo:
the Kiddush [sanctification blessing for Shabbat], the blessings for the Shofar [horn sounded during the High Holidays], the blessings for the Megillah reading [book of Esther read at Purim], and Havdalah [closing ceremony for Shabbat].
Following the tradition of responding to blessings gives the congregation a greater sense of participation in the service.