Before you go, the pilgrim website offers a stage-by-stage account of all the various Caminos; the Camino Guide has detailed maps and information on places to stay and eat along the Camino Frances.
At a church at the start of your chosen route, pick up a credencial (passport) or download the new digital version. There is one for spiritual pilgrims, another for cultural pilgrims. The credencial is stamped along the way, and allows you to sleep in the hostels (albergues) and get a certificate in Santiago.
To earn either one you must have walked at least 100km (which is why Sarria, 111km from Santiago, is a popular starting point); or have ridden on horseback 150km, or cycled 200km. Many people do sections over the years, using the same credencial.
On the Camino Frances, the hardest stretch, but scenically the most beautiful, is the walk up from St-Jean-Pied-de-Port to Roncevalles, followed by the ascent into Galicia from Villafranca del Bierzo to O Cebreiro. Much of the rest is fairly flat; the stages through the plains of Castile between Leon and Burgos have little shade.
If you don’t fancy walking some or all of it, or don’t have time, there are buses and often trains to take you between towns. For an indulgent splurge, go by Spain’s first luxury train – El Transcantabrico Clasico – which starts in San Sebastian and takes eight days, seven nights, calling at all the most beautiful towns of Northern Spain (including Santander, Bilbao and Santillana del Mar) before arriving in Santiago de Compostela.
Whatever route you take, it gets crowded in July and August and finding accommodation can be hard – a good reason to book a tour with a guaranteed bed at the end of each day (plus the added bonus of luggage transfers and support along the way).