(1) Someone should not stand up to pray unless he is in a serious frame of mind. The original tzadikim ones used to wait one hour and then pray, in order to direct their hearts towards the one reciting Shemoneh Esrei, even if the king greets him, he should not respond to him, and even if a snake wraps around his heel, he should not interrupt. (2) Mention the request for rain in Techiyat HaMeitim; and ask for rain in Birkat HaShanim; and Havdalah in Chonein Hada'at. Rabbi Akiva says: One recites it as a fourth blessing by itself. Rabbi Eliezer says: in the blessing of Modim. (3) One who says [in prayer]: "A bird will get to its nest!" and "On the good shall Your Name be mentioned!" "Thank you, thank you"--silence him. One who leads the prayer service and makes a mistake--replace him with another. And he should not refuse at such a time. From where should begin? From the beginning of the blessing in which made a mistake. (4) One who leads the prayers should not repond after the Kohanim "Amen", because of the lost concentration. If there is no Kohen there besides him, He should not recite the Priestly Blessing. But if he is confident that he will recite the Priestly Blessing and return to his prayer, permitted. (5) One who is praying, and makes a mistake, it is a bad sign for him; and if he was a chazan of the congregation, it is a bad sign for his congregants, because a person's messenger is like himself. They used to say about him, about Rabbi Chanina ben Dosa: When he would pray for the sick, he would say: This one will live and this one will die. They said to him: How do you know? He replied to them: If the prayer is fluent in my mouth, I know that it has been accepted; and if not, then I know that it has been torn up.