To make cards you can use GoldenDict or Rikaitan. There are also tools that help create cards depending on the type of media. For movies and TV shows, I recommend mpv scripts. For manga, refer to my Mining from manga article to set up OCR. When you can't use the sentence you've encountered the word in, try to find example sentences online.
When it comes to what card templates to use, before 2020 I used to recommend sentence cards. Now I don't recommend sentence cards anymore. Instead, I recommend using TSCs and SWCs depending on the context. For details, see Discussing various card templates.