Daily Halacha

1. Chazal viewed the recitation of Amen very highly and compared its recitation to a signature that attests to the validity of a document. In fact, Chazal tell us that responding Amen is of greater significance than reciting the Beracha. The failure to recite Amen is considered a gross transgression, while responding Amen with great concentration opens the gates of Gan Eden.
2. The letters of Amen are the root letters of the word אמונה, belief or trust. By responding Amen one declares: "I believe in the blessing that I have just heard and I affirm its truth." Additionally, when responding Amen one should have in mind the beginning of the Bracha, "Baruch Atta Hashem", that Hahshem's name is Blessed. Thus, for example, when responding Amen after "Magen Avraham", one should have in mind, "The Name of Hashem should be blessed, and it is true that He shielded our forefather Avraham, and I believe it".
3. One should answer Amen to any blessing one hears whether he wishes to fulfill an obligation, or even if one overhears a Beracha. One should respond Amen after each line in Bircas Hamazon that begins Harachaman. Moreover, the obligation to respond Amen even applies to a Bracha that does not contain Hashem's Name, such as answering to a Mi Sheberach.
4. The proper intention of the word Amen changes with the Beracha. When answering Amen to Birchot HaMitzvah or Birchot HaNehenin (Berachos on enjoying things), one's intention should be to affirm the truth of the Beracha and his belief in it. When answering to Birchot HaShevach, one should have in mind that he is affirming the truth of that praise. When responding Amen to תפילות one's Amen should be an entreaty to Hashem to fulfill that prayer. At times, Brachot can have multiple purposes and as such one should have multiple Kavanot.
5. When reciting Kiddush on Friday night, we say the words ויהי ערב ויהי בקר quietly before saying יום הששי. In truth, ויהי ערב is actually the second part of the Passuk which precedes יום הששי. We don’t say those words out loud because the first letters of יום הששי ויכלו השמים form the name of Hashem-הויה. While we generally avoid reciting Pesukim in ways which differ from their presentation in the Torah, nonetheless we only say the second part, and don't say the first part of the Passuk quietly because Chazal understand the "טוב מאד" as a reference to death.