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

"It is important to be aware of the cultural norms in Leiden. It is considered rude to be late for appointments or social engagements, so it is important to be punctual. It is also important to dress appropriately for the occasion, as dressing too casually or too formally can be seen as disrespectful. Additionally, it is important to be aware of the local customs and traditions, and to be respectful of them. It is also important to be aware of the local language, and to avoid speaking English too loudly in public. Finally, it is important to be aware of the local laws and regulations, and to abide by them," said another expat in Leiden, The Netherlands.