During the Aseret Y'mei T'shuvah (10 days of repentance from Rosh Hashanah through Yom Kippur):
Traditionally, congregations continue reciting S'lichot each morning before shacharit. When reciting every Kaddish, the words "l'eilah min kol," are changed to "l'eilah u'l'eilah mi-kol."
When reciting the Amidah, include passages marked "Between Rosh Hashanah and Yom Kippur."
We continue to conclude our Shacharit and Ma'ariv services with Achat Sha'alti (MT 662).