any good advice on sim card in spain?

It has come to that I am going to spain next week, as of today I have never been there, I am going to be there for about an week ( and its a personal trip), so I wanted to if any body has been there before ? if you have how much does prepaid card for calling and for internet use only costs ? and how to get em.. please let me know here..... I am there for week, my use of calling will limited to at least 1 hour a day and I need constant internet on my tablet so I guess 1 gb will be fine can any body help??