The person making or responding to a Salaam should do so verbally and not just suffice on nodding the head or waving the hand, etc.

It is preferable that the response be better. In other words, if the person making Salaam says: “Assalaamu Alaikum”, the person responding should preferably say: “Wa Alaikumussalaam Wa Rahmatullahi Wa Barakaatuh”. (One should not add any other words to this)

If one person from a gathering makes Salaam, this Salaam will suffice on behalf of everyone in the gathering. Similarly, if one person from among the gathering responds to a Salaam, the response would suffice on behalf of the entire gathering.

(Source: Aadabul Mu’aasharat - Urdu)