I walked the Camino Ingles as my first camino last year and wondered where to get stamps initially. Getting into the habit of asking anywhere you stop helps a lot. Looking back at my credential stamps came from tourist offices, council offices (they usually are easy to find in the centre of towns/villages with flags outside), every coffee or restaurant stop, the albergues or other accommodation. If you are stuck you can ask in hotels or shops as you arrive in the place you might be staying. I managed to get 2-4 stamps each day without much effort.
All the very best with your camino!