Tickets can now be bought by credit card over the phone. See www.soccer-spain.com for more info. If this is not possible for you,then you need to go to the stadium a couple of days before the game. If they have any tickets for general sale you can get them at the Taquillas at the southern end of the ground. You will be offered tickets by touts as you walk there, dont buy until you visit the taquillas to see if its sold out. If it is, then you can either take a chance with the touts, ( it is possible you will be refused entry if you have a ticket belonging to a Socio who has given up his ticket for the game, though unlikely, if you go in when it's buy at the turnstile), or try localidades-galicia, a ticket agency just off Pureta del carmen, near Sol.

Anywhere in the ground except the bottom tier of the southern end will be ok for you, derends what you want to pay really.

I'm gonna have to start charging for my footy advice