I always wanted to use it but I never felt it worth the daily effort.
Otherwise, if you use something frequently, you won't need effort to recall it.
In programming, I've found that putting in the effort to make flashcards can help guide understanding. - Understanding some thing is easier if you can recall some basic facts of the domain. And at least, taking the time to break some concept down into basic facts will show what you're familiar with and unfamiliar with.
I dump in everything I care about: command syntax, architecture, diagrams (image occlusion), Udemy course material, etc.
It's amazed me the difference it makes versus having to pause and Google all the time. You're faster, you're more competent, and you're better prepared to speak persuasively on the topics you study.
I only wish I had found it sooner. Highly recommended.
* Vocabulary in different fields
* Concepts in maths, physics, comp.sci.
* Geography
* People I want to remember (both historical and more distant relationsships)
* Some useful numbers (e.g. visa card number)
* Silly things (like the periodic table)
* Programming languages (syntax and similar that I might otherwise forget, and useful standard libraries and third-party libraries)
* Useful tools and ideas/concepts I want to remember
I make my cards atomic. No long answers. And I avoid having a large workload - I add new cards at a rate such that I review about 60 +- 30 cards per day. It takes me ~15-20 minutes, and I find it very much worth the effort!
Definitions of rarely but repeatedly encountered terms is the most useful one.
Note that it's only a daily effort the first few days. Over time a single card takes like a dozen repetitions (depending on the complexity).