A class can only take you so far. I took four years of Spanish when I was in school, and then spent 2 months in an intensive Spanish course ( several hours a day, every day ). I still felt very much the same as you do now. Then I went to a place where I lived, worked, and socialized with native Spanish speakers from several different countries - within 6 months, people I spoke to on the phone thought I was born and raised in Colombia.
The best way is complete immersion with real Spanish speakers. It also requires good social skills to connect with those people in a way that actually changes the way you speak and think to sound more natural in that language. People don't follow text-book rules in their own language.
This is true - if you really want to learn a language you have to go to the country and speak the language. I'm fluent in English because I lived in London for three years, and spoke the language every day from dusk till dawn.
I also lived in Spain, but never became fluent in the language because I spoke English to everyone. Immerse yourself in the language, speak to natives all the time and you'll be fluent in 6 months.
Most people are actually really helpful if they sense that you're trying to learn their language and make an effort.
But as everything else in life you have to be determined if you want to succeed. Talk to the storeowner when you go shopping, find a coffee shop you like become a regular and start chatting to people and become known as that guy that's learning to speak Spanish, get a native girlfriend, get a job where you have to speak the language, etc.
Take advantage of the fact that people love their own culture. Ask them about it, and they'll see you're trying to learn (and not just being some pompous foreigner). It's also a good chance to learn more about the culture anyway.
The best way is complete immersion with real Spanish speakers. It also requires good social skills to connect with those people in a way that actually changes the way you speak and think to sound more natural in that language. People don't follow text-book rules in their own language.