Ask HN: How do you memorize syntax and common API for a new language?

I'm sure a lot of people here will recommend doing a lot of side projects, but is there a more boring yet effective way? Similar to flash cards instead of writing for vocabulary. The biggest contextual block from coding with an unfamiliar language is the syntax and basic API.

If I could draw an analogy, it would be trying to learn a language in a foreign country without any fundamental understanding. I find it much easier to absorb new materials when I have a basic set of common phrases memorized beforehand.