Anki is spaced-repetition software. It works on the basis of the 'forgetting curve'. The idea is that new information is soon forgotten but if you remind yourself an hour later, you'll remember till the next day; and if you remind yourself the next day, you'll remember till next week; and if you remind yourself next week, you'll remember for a month, etc.
I've heard that one of the better ways to use Anki is creating your own decks. Personally, I find this to be a lot of effort. Too much for me to bother making individual cards.
I am experimenting with new ways to make cards. I'm no expert but here's what I have found.
The first way is to use Google sheets. In column 1, include a native language word or phrase. There's a formula to translate each of these into your target language using country codes.
For English to Spanish, click cell B1 and enter =GOOGLETRANSLATE(A1,"en","es"). Tap enter. Now click cell B1 then click and hold the 'drag button' in the bottom right of the cell and drag this down column B to the end of the list in column A. This should translate everything. English column A, Spanish column B.
Save the document as a csv file with text separated by tabs or semicolons. Open the Anki app, create a new deck, and import. Find the csv file, play with the settings. Voila.
One way of making lists of useful (to you) words is through Calibre. Put an ebook that you want to read into calibre. Find it in the list, right-click and press 'Edit book'. When the new window opens, click Tools > Reports > Words. Sort by 'Times used'. This arranges all the words in the book by frequency. You can copy this list into Google sheets, as above. If you're new to the language, sort by most frequent as you'll get a better payoff for the effort.
(Be warned that a lot of high frequency words are functional and/or have many, many meanings. If e.g. Spanish is a new language, one or two key definitions is fine to start with. You can add nuance later. You can also delete the proper nouns: e.g. you don't need a translation of 'Marx' if it's the same in both languages.)
If you have a better vocabulary, scroll down and grab the words that are used only e.g. 8, 7, 6, 5, 4, 3 times in the book. Getting Anki lists like this, you can front-load the vocabulary for a book that you want to read and memorise the relevant vocab on the bus or the toilet.
(What does Lenin's Imperialismo: fase superior del capitalismo look like word frequency-wise? The top 12 words are de, la, en, el, los, y, que, del, a, las, se, por. The most frequent substantive word, at number 13, used 369 times, is 'desconocido'. Later comes 'Capital' m, used 207 times. 'Imperialismo' 183. 'Bancos' 170. 'Millones' 155. 'Capitalismo' 131. …)
If you read the book at the same time, you'll recognise the vocab as you read. (It might take a long time to come across the less frequent words—one that's only used once might be on the last page.)
Another way of creating lists is using your favourite song lyrics. Get these from a search engine, search for 'song name+letra' then search for the 'song name+lyrics English' to see if there's a translation. If not you can decide how fun it will be for you to translate it yourself or you could use the Google sheets method. Then put one language in one column and the other in the next column. If you have a translation, you can probably use any spreadsheet software. But the cvs file needs to be in UTF-8, I believe.
Another method involves reading books on Kindle. Every time you don't know a word or sentence, click it and get the translation. Then either highlight that word or the whole sentence (for context). Once finished with the book (because it's too hard, boring, or you get to the end) the highlights ('notes') can be exported. (If you read through your notes to recap all the words/sentences that you struggled with, and do it again a week later, it's spaced repetition.)
There's also a way to transfer these notes into Anki cards. There are some scripts/programs in GitHub that could be useful for this. I've not played with it yet but VocabSieve should allow you to import Kindle lookups, translate them, and export this data as a file that can be imported to Anki.
With all these methods, you kind of have to trust the translation software. I've found it to be good enough for English to Spanish. The odd translation is obviously wrong but otherwise, it's fine.
Hopefully these help someone else to avoid the tedium of making Anki decks but in a way that ensures the vocab in your decks is relevant to you.
You can, of course, do things the not-so-old fashioned way. Rather than importing your vocab to Anki, use your spreadsheet. You'll just have to work out the timings for yourself. Then you could hide the first column, and type the translation of the word in the second column into the third column. The next day, hide the first two columns and type the translation of the words in the third column into the fourth column. You can change the colour of rows of words that become too easy and create a colour-coded system for reviewing these monthly, yearly, etc.
What happened there?
I'm curious.