No vaccinations are necessary for entry into Portugal. It is advisable to bring enough prescription medicine and insurance to last the duration of your stay, as there might be problems when purchasing medication. Airport custom officers keep a close watch for any illegal drugs being brought into the country.
When invited to a Portuguese home, it is considered polite to bring sweets for the children or flowers for the hostess. Do not try to jump the queues at bus stops, and avoid stretching on the street or at a meal as it is considered rude. Stay away from any discussions about football and wear proper attire when visiting religious monuments.
Tip taxi drivers about 10% of the fare. Restaurant waiters are viewed as professionals and a tip is considered as a token of appreciation, not a way to compensate their wages.
Portugal is a very safe country, but petty theft can be a slight concern in certain areas of Lisbon and Porto unless one is vigilant.