Ask HN: What's the Smartest and Quickest Way to Learn a New (Spoken) Language?

I've decided I'm going to learn a brand new language as my "Personal Challenge" for 2017.

Candidates are German, Spanish, and last preference Gujarati (my Dad's native language).

How do I go about this as an Adult? I want to learn fast, and efficiently. Are there any proven "Language learning Hacks"? I saw Ankhi or Ankha cards mentioned on some forums. Not sure that will work for me.

Please, give me some hacks or tricks you've used personally to successfully learn -- to read and speak -- a new foreign (to you) language. Also timelines - i.e. how many hours or days or months of time investment to see noticeable results, which would be that I understand someone speaking in that language, and also am able to respond / speak back my response in the same language.