"Who answers Amen with all his might, to him the gates of Paradise are open." ~~ Talmud, Shabbat
"One who stands [in prayer] in Eretz Yisrael (the land of Israel) should direct his heart towards Jerusalem, if he was standing in Jerusalem, he should direct his heart towards the holy Temple. " ~~ Talmud, Berakhot 27a
"The gates of prayer are sometimes closed, but the gates of repentance are forever open." ~~ Midrash Deuteronomy R. 2:7
"The prayers of the sick are more effective than the prayers of others, and are answered first." ~~ Rashi
"Unless we believe that God renews creation every day, our prayers grow habitual and tedious." ~~ Baal Shem Tov
"The prayer of the sick for himself will avail more than any other. " ~~ Genesis (Bereshit) R.
"All are equal in prayer before the Lord. " ~~ Exodus (Shmot) R.
"Any study of the Torah and any prayer unaccompanied by good deeds and repentance void the Torah and make the prayer unwanted." ~~ Otiyot Derabbi Akiva
"The best weapons of Jew are his prayers." ~~ Nachman of Bratslav
"But how can you say, “It was only talk, so no harm was done?” Were this true, then your prayers, and your words of kindness, would be a waste of breath." ~~ Nachman of Bratslav
"Who prays in Jerusalem is as one praying before the Throne of Glory, for the Gate of Heaven is there." ~~ Pirke Derabbi Eliezer
"Eating is the best of prayers." ~~ Avrunin