Avinu Malkeinu is customarily recited during Shaḥarit and Minḥa, following the ḥazan’s repetition of the Amida. This prayer is very powerful, as in it we turn to God from within two different types of relationships with Him: as children to their father and as servants to their king. The Gemara tells us that a fast was once declared because of drought. Many people’s prayers went unanswered. Rain did not fall until R. Akiva led the prayers, declaring: “Our Father, our King, we have no king but You. Our Father, our King, have mercy on us for Your sake.” To emphasize the importance of this prayer, it is customarily recited while standing. Many also open the ark during its recitation. Avinu Malkeinu is recited even when Taḥanun is omitted, such as in the presence of a newlywed or of a father on the day of his son’s brit (Rema 602:1). Even someone praying on his own may recite Avinu Malkeinu (Be’er Heitev 602:1; see Da’at Torah 584:1).
After Pesukei De-zimra and before Barkhu, most communities, following Arizal, add the psalm “Shir ha-ma’alot mi-ma’amakim” (Tehilim 130). It is not recited in Yemenite (Baladi) communities, and several Ashkenazic communities omit it as well, so as not to interrupt between Pesukei De-zimra and the berakhot preceding Shema. (See MB 54:4.)
It is permitted to get married during the Ten Days of Repentance. True, some great Ashkenazic rabbis maintain that weddings should not take place then, as it is meant to be a somber time (Mateh Ephraim 602:5; Kitzur Shulḥan Arukh 130:4). However, Sephardic communities do not share this concern, and even some Ashkenazim get married during this period. Therefore, weddings may be scheduled for the Ten Days of Repentance. There is even a certain advantage in entering Yom Kippur having just done this great mitzva (Sdei Ḥemed, Aseifat Dinim, Ma’arekhet Ḥatan Ve-kalla, klal 23; Melamed Le-ho’il EH §1). However, they should be pay special attention to ensuring that the wedding does not include immodest mingling of men and women.