EU citizen: moving to Luxembourg

Do I have to register, and when?

What the law says

With a valid ID card or passport you can stay for up to three months (Art. 5).
Beyond three months you must be working (employed or self-employed), or have enough money and health insurance, or be a student with money and insurance (Art. 6).
To stay longer than three months, ask your commune of residence for a registration certificate within three months of arriving (Art. 8).
The certificate is handed over immediately once you show the documents (Art. 8).

The certificate does not create the right of residence: meeting the conditions of Art. 6 is what counts (Art. 8).

By practice area, language and town, in a neutral order.