7. [Regarding the choice of a person] to lead the Selichos, and the High
Holiday prayers, the congregation should be discriminating ("yedak'deku"),
and choose a highly respectable man, who is a great Torah scholar, and who
is known for performing good deeds, to the extent that it is possible to
find such a person. He should be at least thirty years old, for by then,
his hot-blooded passions of his youth will have subsided, and his personal
desires will have been subdued. He should also be married, with children,
for then he will pour out his heart, and beg for mercy from the bottom of
his heart (1).
Similarly, [regarding the choice of ] a person to blow the shofar [on Rosh
Hashana], and a person to prompt the shofar blower, the congregation should
be discriminating, and choose men who are G-d fearing, Torah scholars.
However, any male Jew is eligible to perform all [the aforementioned
functions], provided he is acceptable to the congregation. If one sees that
[one's appointment] will cause a quarrel, one should withdraw oneself, even
though someone unsuitable will take the position.
(1) If there is a choice between a G-d fearing, Torah scholar, who is
single and less than thirty, and a married man above thirty, who is not a
Torah scholar, the job should be given to the Torah scholar (Mishna Berura