2002 CF: 2004 from Paris: 2006 VF: 2007 CF: 2009 Aragones, Ingles, Finisterre: 2011 X 2 on CF: 2013 'Caracoles': 2014 CF and Ingles 'Caracoles":2015 Logrono-Burgos (Hospitalero San Anton): 2016 La Douay to Aosta/San Gimignano to Rome:
I prefer to have an idea of where I would like to stop each day. This year I have planned to walk an average of 20kms per day by using http://www.godesalco.com. On this website you can choose how far you want to walk each day and the website offers a printed itinerary with mileages, progressive mileage, symbols for accommodation available etc. It also offers a print out of every town and village so even if you walk further you know where the refuges are. You can also download a profile of the route you are walking.
There is no way of ensuring a bed if you plan to stay in the refuges but there are usually small hostales or fondas to stay in if the albergue is full.
I was very careful in planning what to take with me, but didn't plan an itinerary more than a day or two in advance. That way, I could easily vary the distance walked based on how I felt at the time. I had some 10km days, and some 35km days. I doubt I would have planned either in advance.
You can't do much to guarantee that you'll get a bed, but it's really not worth worrying about. You'll find somewhere to sleep, even if it's on the floor somewhere.
I've got a rough idea but only based it on having done it all before:
SJPdP - Roncesvalles
Roncesvalles - Larrasoana
Larrasoana - Cizur Minor
Cizur Minor - Puenta la Reina
Puenta la Reina - Estella
Estella - Los Arcos
Los Arcos - Logrono
Logrono - Najera
Najera - Santo Domingo
Santo Domingo - Belorado
Belorado - Atapuerca (or possibly Cardenuela Riopica)
Atapuerca - Burgos or Tarjados
Burgos - Castrojeriz
Castrojeriz - Fromista
Fromista - Carrion de los Condes
Carrion de los Condes - Terradillos (or if I'm feeling stupid Sahagun)
Terradillos - El Burgo Ranero
El Burgo Ranero - Leon
Leon - San Martin
San Martin - Astorga
Astorga - Foncebadon
Foncebadon - Ponferrada
Ponferrada - Villafranca whatsitsname
Villafranca - La Faba or O Cebriero
La Faba - Triacastela
Triacastela - Barbadelo
Barbadelo - Hospital de la Cruz
Hospital de la Cruz - Melide (or somewhere else that's less grotty!)
Melide - Pedrouza
Pedrouza - ... SANTIAGO!