Initiating the Salam is an act of Sunnah (whatever is reported from the Prophet). It is a way of honoring one another, reminding Muslims of their Creator Who is called "Al-Salam". It unites Muslims' hearts, spreads love among them, and involves asking for safety for them. It is authentically reported in Sahih Book of authentic Hadith by
Muslim on the authority of
Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace be upon him) said,
"By Him in whose Hand my soul is! You will not enter Paradise until you believe; you will not (truly) believe until you love each other. Shall I show you to something that if you observe it, you would surely love one another? Propagate the “peace” (Salam) among you."
(Part No. 24; Page No. 118)
returning Salam must be with the same wordings and adding more words is a Sunnah. Allah (Exalted be He) says:
When you are greeted with a greeting, greet in return with what is better than it, or (at least) return it equally.
It is related by
Al-Tirmidhy on the authority of
`Imran ibn Al-Husayn (may Allah be pleased with him) that
A man came to the Messenger of Allah (peace be upon him) and greeted him saying, "O Messenger of Allah! Al-Salamu `Alaikum (peace be upon you)" and he replied to him. When the man sat down, the Prophet (peace be upon him) said, "Ten (good deeds)." Another man came and greeted him saying, "O Messenger of Allah! Al-Salamu `Alaikum wa Rahmatullahi", and the Prophet (Peace and Mercy be upon him) replied. When the man sat down, the Prophet (peace be upon him) said, "Twenty." A third man came and greeted him saying, "Al-Salamu `Alaikum wa Rahmatullahi wa Barakatuh (Peace, Mercy and Blessings of Allah be upon you)", and the Prophet responded to him. When the man sat down, the Prophet (peace be upon him) said, "Thirty".
As for returning Salam by saying "Hi" and "Hello", this is not sufficient.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.