Ask HN: What are some efficient ways of learning a new programming langauge?

What are some strategies people on HN employ to learn and retain as much of the syntax, concepts and intricacies of a new programming language?

I always find learning a new programming language harder and cumbersome, compared to learning a new spoken language.

How, if at all, do you successfully employ methods like "spaced repetition" (Anki), "memory palaces", note taking and exercises? In a nutshell, how does one learn and retain as much of a new programming language in an efficient way?