Saying the blessing? One is to designate an area from the dough that the Challah will be separated from. Then one is to say the blessing of “Lehafrish Challah”. One then separates a Kezayis of dough and says “Hareiy Zu Challah” or “This is Challah”. If one separated the Challah prior to the blessing one may still say the blessing if he [or she] has not yet said “Hareiy Zu Challah”.
 Some have the custom to add “Min Haisa” [see Taz Yoreh Deah 328:1]
 As applies by all Mitzvahs that the blessing is said prior to the Mitzvah. [Chochmas Adam Shaareiy Tzedek Mitzvos Hateluyos Baretz 14:32; So writes Hakashrus 14:20; “Spice and Spirit”] However Piskeiy Teshuvos 242:11 records that one is to only say the blessing after completely separating the Challah from the rest of the dough in order so no part of the Challah remains on the dough if one were to separate it after the blessing. See also Rav Akiva Eiger 328:1 and Piskeiy Teshuvos 457:1
 Rav Akiva Eiger 328:1 in name of Raavad, in name of Rav Acha Gaon; Beis Yosef 228; Rashba Chulin p. 94; See Admur 457:18 “All the sanctifications of Teruma and Maaser is through speech…One calls it the name Challah”; Admur 527 KU”A 2 based on Tosefta in Teruma chapter 3 “Although Terumah is sanctified with thought alone, if one plans to call it a name the food is not sanctified until one does so”
Bedieved if was not said: If one did not say “Hareiy Zu Challah” but had in mind for it to become Challah, it is valid. [Admur 4578:18 in parentheses “Or even thought about it alone”; Admur in KU”A ibid; Michaber Y.D. 331:46 regarding teruma; Implication of Setimas Haposkim who do not mention the need to say Harei Zu Challah.]
 Hakashrus 14:21
 Hagahos Maimanis ibid
 The acronym of the name Chana stands for Challah; Nida and Hadlakas Neiros. In merit of her fulfilling these three Mitzvos properly she had her prayers answered and had a son Shmuel which was a prophet and leader onto Israel. Thus, each woman should Daven upon separating Challah to have children that are proper and G-d fearing. [ibid]