The Ba’al Tokei’a
The one who blows the Shofar (Ba'al Tokei’a) should be a righteous and learned person. He should review the Halachic and (if possible) the Kabbalistic aspects of blowing the Shofar beforehand (see below).
In addition, the Ba'al Makri (the one who points [or reads] to the Ba'al Tokei’a as to what sound to blow) should be a righteous man who is fluent in the laws and meanings of the blowing of the Shofar.
The Shofar
The shofar should preferably be a ram’s horn. The horns of other kosher domestic animals are also acceptable except for those of a bull or ox.
Non-Yemenites should not use shofars made from the horns of Kudus if there is a ram’s horn shofar available.
The shofar must be longer than a Tefach (handbreadth) so that it is visible on both sides of the ba’al tokei'a’s hand when he is blowing it.
A cracked shofar may be disqualified. One should not use it unless he ascertains its precise Halachic status.
No Talking
The entire congregation should listen to the brachot and the blowing of the Shofar and keep in mind that they want to fulfill the Mitzvah. One should not say Boruch Hu Uvaruch Shemo during the recitation of the brachot. The brachot of the Shofar extend to and include the Shofar-blowing during the Musaf Amidah and the repetition of the Amidah. It is therefore not proper to talk until the end of the Shofar-blowing at the conclusion of Musaf (unless it is necessary for the davening or the Shofar-blowing).
During the pauses in between the three sets of Shofar notes, one should think thoughts of Teshuvah. (It is not the Chabad custom to articulate any words at this time.)
