What is the minimum extent for initiating the greeting of peace, and is it sufficient to say only "Salam" while still receiving the reward for it, and how does one properly and sufficiently return the greeting of peace?

Spreading greetings (salam) among Muslims is one of the outward rituals of Islam and a means of love and harmony. The minimum is saying "salam" to the one greeting and "salam" to the one responding. The better is "As-salamu alaykum" (peace be upon you) and "Wa alaykum as-salam" (and peace be upon you). Returning the greeting should be with something similar or better. As for merely responding with "Wa alaykum" (and upon you), some scholars hold that it is sufficient, while others believe it is not a complete answer, even though Shaykh al-Islam Ibn Taymiyyah preferred its sufficiency if the full phrase "Wa alaykum as-salam" is implied. It has been narrated from the Companions what indicates the sufficiency of responding with "Wa alaykum"; however, one should not limit oneself to it when responding to Muslims, because it is the commanded response when greeting the People of the Book.