How do I quickly and efficiently learn a new language?

you can keep 5 new words daily and use website for beginners which will guide you step by step to learn faster and smarter ...also listening to radio is a very good way to be familiar with the new language

Just Learn 100 daily used words of a language and try to use them routine wise.

Don't try something hard to achieve, try something smart or different to achieve 

1.Make a friend who can speak better and chat with them,

2.Live in the place where you can find more people who speak that language

3.Watch movies

Create an atmosphere, i.e. have as much natives as you can around you, watch and read shows in that certain languages. read literature in that language, don't forget that books can never be replaced. 

By talking and asking someone whom has the native language or knows the language you want to learn.