Rosh Chodesh Tevet is the only time the full-Hallel is said on Rosh Chodesh. (Usually on Rosh Chodesh we leave out 2 half-paragraphs.)

Between Shacharit and Mussaf we will take out 2 Sifrei Torah. First we call up 3 people to the Torah for Rosh Chodesh and then – in the second Sefer Torah – a fourth person for Chanukah.

We then daven Mussaf for Rosh Chodesh, with Al Hanisim.

Starting tonight – Monday night – don’t forget Ya’aleh Veyavo and Al Hanisim in the Amida and Birkat Hamazon.

Source: Kitzur Shulchan Aruch 139:24