Use Google Webmaster Tools to set the geographical location of your site as Spain.
Use a host based in Spain.
Get backlinks from Spain based website and try to get them from pages that themselves have high PR.
And yes, more and more content about Spain like Nick said
Nick, Angilina, thanks. I went into my Google account and set the geo preference for Spain. "Logically," I hope that doesn't hurt its rankings in other potentially rewarding regions.