I have family in Spain and was considering moving there. I've heard of dual citizenship, but can't find anything for Spain. I don't exactly want to give up my American citizenship, but am considering it if I need to. How do I apply to find out if I am even eligible?

Dual citizenship is only for people who are citizens of one country, and parents were born in another country. So unless your parents were born in spain, dual would not apply to you. For instance my son was born IN the US to Canadian parents, so therefore he has dual citizenship and two passports US and CDN; so no, you are not eligible for dual citizenship.

Giving up your US citizenship would mean giving up your benefits should you have any. It only means you have to return to the US once a year.