Best Way to Learn a Second or Foreign Language?

Is there one best method to learn a language? If you are a child, I'd say it's the immersion method. Living the language, children learn a second language about the same way they learned their native language. If you are an adult (post-puberty, more or less) learning a second or foreign language, it's a different story. There are so many different variables involved, that it's hard to say what would be the best method. Here are some of the possible variables: the learner's motivation, personality type, aptitude for language learning, learning style, what language the learner is hearing and speaking outside class, how the learner views the language being learned, the teacher's personality and style, the teaching materials. These are only a few of many variables involved in language learning. So when asked what the best method is to learn a language, maybe the best answer is "it depends."