The Second-Best Way to Learn a Foreign Language
This is not The Best Way to Learn a Foreign Language. The best way is total immersion. This is the Second-Best way. It does not involve the spoken aspects of the language, because that falls in the domain of the best way. This way involves a few simple steps.
Step one: Take a class.
Many people would say that taking a class is the worst way to learn a new language. Those people may be correct, but if you take a class then you will have an instructor at your disposal. This is important. You cannot learn a new language entirely from a textbook. There are idioms to learn, exceptions to standard syntax, non-standard spelling conventions, and usually a lot of accents and diacritical marks to learn about. You will need someone to ask about this sort of thing, and a good College Spanish Professor should be a good resource.
Step two: Take a genuine interest in learning the new language.
If you don't have a genuine interest then you won't succeed with anything short of moving to Madrid. If you are genuinely interested in learning the new language you are more likely to start thinking about the language during your day when you are not in a class or studying. Have fun with it. Look up the words that they aren't teaching you in class or in a textbook. Use new and interesting adjectives. Insult people. It can be fun.
Step three: Buy some books in your new language.
No, not textbooks. If you are studying Spanish, you should buy Cien Años de Soledad, a good book that is critically acclaimed. Haven't you always heard that it is best to read literature in its native language? Translate the book. You will likely need a two-language dictionary and a lot of advice from your professor for this. As you translate you will start to recognize phrases and words that are repeated often. You will likely remember their meanings and not have to look them up too many times. It is best to use a physical dictionary and not an online one for this. The physical act of having to look for the word will make you more motivated to remember it. Also, if you learn your phrases, sentence structure, and choice of adjectives and verbs from a work of much-acclaimed literature then you are more likely to develop a sophisticated and intelligent vocabulary and style of speech. A text book will make you sound like a well-versed kindergartener.
I learned to read and write English with Dick and Jane; my standards have risen significantly since then.