Norwegians like to dress casually at any other time, but on May 17th, they do smarten up. Many (women in particular) proudly don the local 'bunad', the traditional costume, of which there are over 200 different kinds in Norway. Those who don't still dress smartly (this means suit for men, or at the very least a jacket). Sportswear and casual clothes, so popular any other time of the year, are a no-no, and although allowances are made for foreigners, it is worth making an effort to blend in.
Fly the flag
On 17 May Norwegians paint the town red... and white, and blue. The flag is indeed a big part of the celebrations, and your party kit is not complete without one. Thankfully cheap flags can be bought pretty much everywhere in the days before the event, from local supermarkets to discount shops and many other places, so just get one and join in.
Brace yourself for queues
To get a drink. To get a bite to eat. To go to the loo. On public transport. On packed roads. Plan accordingly.
Book your table well in advance
While many Norwegians will grab a 'pølse i brød' (hot dog) or an ice-cream while out and about on the day (it has indeed become a bit of a tradition for many), lots will also sit down for a proper lunch, and many hotels and restaurants offer special May 17th menus. If you really want to make a day of it and enjoy Norway's Constitution Day in style, make sure to book well in advance at your chosen restaurant. Just turning up on the day is bound to bring disappointment.