you tend to find that when using a cash machine in the same network (Telebanco or servired for example) the charges are 30 cents to 1 euro. If you use an inter network (ie your card is servired and you use telebancoo) they will charge you 6 euros a time.
I found this out myself a few years ago. My mother had my cash card as I was in UK and having reforms done on my house here. She was paying the builders by withdrawing funds from my account here in Spain. However rather than go to my bank she went to her cash machine which is literally across the road. In 3 months I was charged in the region of 900 euros for the privelege.
You will also find that cash machines that are not part of a bank (fopr example in a supermarket) will charge a percentage of the amount withdrawn. In my local Caprabo this is 4%/
However they are all required to display any charges they make before you withdraw so you have the option of saying no.
Worth watching out for that one.