The Rules of greeting one Another
Issue 446: It is mustahab to greet one another, but it is wajib to reply to the greeting.
Issue 447: It is makruh to say greet someone who is praying salat.
Issue 448: If someone says salam to one who is in Salat, the reply must be given exactly as it was originally worded; for example, if it is said: (عليكم السلام) the reply must be given as: (سلام عليكم) but if the greeting is (السلام عليكم) the Ihtiyat Wajib is that the reply be given as: (سلام عليكم)
Issue 449: It is not permissible for one who is reading die Salat to say salam to another person (to initiate it).
Issue 450: The reply to a salam must be given immediately.
Issue 45 1: The reply to a salam must be in such a way that the recipient can hear it, but if the one who says salam is deaf or if he gave salams and quickly went away, and if it is possible to reply by a gesture or another way so that the other person can comprehend (your reply), it is mandatory to act in this way, and in any other instance, it is not necessary to reply, and if in the state of Salat, it is not permitted (to reply in another way).
Issue 452: If two people say salam to each other and the same time, then according to Ihtiyat Wajib, both must reply to the salam of the other.
Issue 453: It is mustahab that one who is riding should great the one who is walking, and the one who is standing should greet the one who is setting, and a small group of people should greet a large group of people, and the younger ones should greet the older ones.
Issue 454: It is mustahab - except in Salat - to reply to the salam in a better manner, so then if someone says to you (سلام عليكم) it is mustahab to reply by saying: (سلام عليكم ورحمة الله)
Issue 455: It is makruh for a man to say salam to a woman, especially a young woman.