Yesterday - 3 Tammuz - was the day that יְהוֹשֻׁעַ told the sun and moon to stop orbiting, as recounted in Sefer Yehoshua Ch.10, verses 12-14.
Kiddush Levanah - (blessing on the new moon) - can be found in any Siddur; usually after the Ma'ariv service.
Men have an obligation to say Kiddush Levanah every month. The custom is that women do not say Kiddush Levanah.
Kiddush Levanah cannot be said before the new moon is 3 days (72 hours) old. Some even wait until it's 7 days old.
Kiddush Levanah can only be said while the moon is waxing.
Kiddush Levanah should not be said while standing under a roof. However, if this is impossible or impractical, then it can be said inside by a window.
Source Kitzur Shulchan Aruch 97:7, 8, 10
Sunday, 4 Tammuz 5775