Everyone who walks the Camino should get familiar with the following Spanish terms:
A compostela is the "pilgrim certificate" you get at the end of the walk if you've completed 100 kilometers (about 62 miles) or more on foot. If you are not Catholic, but did the Camino for 'spiritual reasons' you can get a compostela. If you say your goals were non-spiritual, you get a rather plain certificate of completion.
Albergues and refugios are the pilgrim's accommodation stops. Run by churches, town councils, non-profit organizations, and private for-profit groups, they provide cheap beds in dorm rooms, mattresses in church bell towers, or provide hotel-like rooms with prices starting at five euros a night.
A credential is the 'pilgrim passport' issued by various Camino-friendly organizations. Each albergue or refugio has its own stamp, which you'll receive each night. You need a credential to stay in pilgrim accommodations, and a complete record of stamps to get your compostela. Arrange to have one posted to you in advance if you're not starting at a popular stepping-off point. Accommodations are first come, first served, with preference given first to walkers, then horse-riders, then cyclists.
Craig Martin has been travelling full-time since February 2006 and walked three Caminos in that time: the Camino Francés, the Via de la Plata, and the Camino Inglés. A Kiwi, he loves wine and is addicted to the new. Find more of his travels on his award-winning site, @indietravel on Twitter, or on Google+.