When are you planning to go? It makes a difference as to how far one needs to reserve ahead. Getting reservations from SJPdP at that time would be difficult up to Pamplona in a private room, even at an albergue. Iti is quite crowded.
I use booking.com. It is the best website IMO to make reservations. One can see pictures of the hotel/albergue and then the room itself. It usually even gives you the size in sq. ft. of the room. It has a good map feature where you can look at the location of the establishment. If you signup (free) and make your reservations they put your booking to a trip file where you can access all of your reservations. Cancellation free of charge dates vary by the accommdation. Some reservations can be cancelled on the same day , others vary from 3days to several weeks. Having all the information in one account makes it easy to change dates and juggle reservations. Hands down, it is more user friendly than Hotels.com or Agoda.com. Look also at the recommendations from clients. Many of them in the small towns on the camino are from pilgrims.
Gronze.com lists additional albergues as well as some accommodations that booking has. What I really like about Gronze are its camino maps and altitude information.
Brierley’s CF guide provides similar maps but you can get much of that info by using Gronze online.
Lastly, if I am iffy about whether to stay at a place, I go to Tripadviser.com
Sometimes you will find information regarding the establishment and additional feedback from customers.
I also use Rome2rio for public transportation planning along the routes. In addition
@Anniesantiago suggested years ago to take a photo of taxi cab numbers as you go through towns on your cell phone so if you get exhausted you can call for a cab. If you are at a bar or cafe, you can ask them to call as well.
Good planning and keep the questions coming.