What are the rules for Tet?

Could you elaborate on the traditional rules and customs surrounding the celebration of Tet? As a cultural holiday deeply rooted in Vietnamese culture, Tet is often considered a time for family reunions, feasting, and honoring ancestors. I'm particularly interested in knowing if there are any specific practices or taboos that individuals should observe during this festive period. For instance, are there any specific foods that are traditionally eaten, or are there any activities that are considered auspicious or inauspicious? Additionally, how do Vietnamese people typically greet each other during Tet, and are there any specific greetings or phrases that are commonly used? Understanding these aspects would help me gain a deeper appreciation for the cultural significance of Tet.