How to learn a language

Leaning a language requires an enormous amount of dedication and hardwork. Obviously, knowing a language has many levels. General perception of language mastery though is usually put at very low, meaning that but just knowing a few phrases, some people claim that they know a certain language.
Firstly, a non-native language can be either classified as ones second or foreign language. A second language is the one that is not a persons mother tongue but s/he has to use it everyday and everywhere. For example a Chinese living in British Columbia, Canada has English as his second language. If he decides to learn Italian in Vancouver, then Italian is ranked as a foreign language. Obviously, usually a person can achieve a high level of proficiency in a second language. That however excludes the accent. Usually, a person retain his/her accent unless s/he is raised as a teenage is the destination country.
To my opinion a very good book on language learning is "how to learn a foreign language" by Pimsleur. Also, for a detailed study of the learning mechanism, the book "developing second-language skills, theory and practice" by Chastain is recommended.