How should a Shaliah Tzibur conduct himself?

Regarding a Shaliah Tzibur who stretches out the prayer so that the congregation hears his good voice, the Shulhan Aruch (O.H. 53:11) says that if he does so to show off or because he takes pleasure in hearing his own voice, it is considered a foul act. If, however, it is because he is gladdened by the fact the congregation can hear him singing praises to Hashem, then he will be blessed. Evidently, even when done with pure intentions the Shaliah Tzibur must pray with a serious attitude and with awe. The Shulhan Aruch continues and says that generally speaking, the prayer should not be stretched out as it is burdensome on the congregation.

The Mishna Berura (M.B., O.H. 53:35), quoting the Sefer Hasidim, cites a related event which shows the gravity of a haughty Shaliah Tzibur. When Rabbam Shimon ben Gamliel was being taken to be martyred, he asked Rabbi Yishmael why he was deserving of such punishment to which the latter replied that is was due to Rabban Shimon ben Gamliel being gladdened and deriving personal benefit when he would give sermons.

The Shulhan Aruch (ibid:13) goes on to say that one whose garments are ripped such that one’s arms-and according to most Rishonim (quoted in the Mishna Berura [ibid:39]), one’s shoulders-are exposed should not go up to be Shaliah Tzibur. Accordingly, a tank-top would be considered inappropriate dress. Rabbi Ovadia Yosef (Yabia Omer, vol. V), quoting different sources, says that even one wearing a T-shirt should not be Shaliah Tzibur, unless the sleeve reaches one’s elbows. Some suggest (See Mishulhan Avotenou, laws of Shaliah Tzibur) that the custom in  Morocco was to be even more stringent and the Shaliach Tzibbur would be meticulous to have his full arm length covered. Although  it is possible that in this instance one can suggest that times have changed and one may rely on the opinion of most Rishonim that as long as the shoulder is covered, one can be Shaliach Tzibbur, nevertheless, it is proper to be strict and have one’s arms covered at least until the elbow.

Summary: A Shaliah Tzibur should not stretch out the prayer unnecessarily with his voice. If he does so, it should be with pure intentions and not out of haughtiness. A Shaliah Tzibbur should wear a shirt whose sleeves reach at least the elbows.