The new kid remembers who said hi on day one. Be that name.

First days are strange because nobody has decided anything about you and you have not decided anything about them. In that gap, one person saying hello does an enormous amount of work, and the person on the receiving end tends to keep that detail for years. It takes about four seconds and requires nothing from you but being the first to move.

If someone new turns up this week, get their name and use it. You do not have to adopt them or sit with them all term. Being the first friendly face is already the whole thing.