Been a while since I did that, but I usually take a course on Udemy. Once, I get hold of the syntax, I request my manager for a feature and started to work on it. Never waited too long to learn a language (a day or two tops), always liked to jump head first into code - of course, this has its own demerits, but I like to hit the ground running fast. Over time, I learnt the language specific nuances.