I first went through the lengthy process of getting an ID card called the NIE that takes about forty days. You will also have to apply for a digital tacho card. Iwont get the card before xmass but I have the paper with he stamp on it, they like that here. It allows me to drive till my offical card arrives.
I then went on the net and got a list of all the transport companies in my area and phoned them. Well my wife did as she is Spanish an I only speak basic Spanish at the moment. Basicaly you have to be here they have a shortageof international drivers and as an international driver it is better that you speak English because you spend more time out of Spain when you are working.
If I can help you with any more info just let me know
Terry