To book accommodations, contact Norwegian State Railways at 011 (+47) 815 00 888 or visit their Web site (see Resources, below). Select 'Oslo' as your 'From' city and 'Stavanger' as your 'To' city, then select your desired date and time of travel.
Choose between economy (Ordinær) and first class (Komfort) seats, the latter equipped with outlets for laptop use and cell phone charging. The Komfort seats are very popular on this run, as it tends to attract a lot of business travelers, so they tend to sell out fast and you will need to book one as far in advance as possible.
Select a payment method (credit cards only: Visa, Mastercard, Diner's Club or American Express) and fill out your contact information, then submit your secure online payment. Norwegian State Railways uses SSL encryption to protect your information from would-be identity thieves.
Pick your tickets up at the Oslo train station from a ticket seller or an automated ticket machine. Another option you may choose is to pick up your ticket on board the train, but this may create delays for others as you try to board the train--and you don't want to upset a Norwegian cowboy!