What cultural faux pas should I try to avoid making in Hanoi?

"It is important to be mindful of cultural norms when visiting Hanoi. It is important to dress modestly and to avoid public displays of affection. It is also important to be respectful of religious sites and to avoid taking photographs without permission. Additionally, it is important to be aware of the local customs and to avoid pointing with your feet, as this is considered rude. Finally, it is important to be aware of the local language and to avoid speaking loudly or using offensive language," remarked another expat in Hanoi, Vietnam.