1. Definitely use Cloze cards. These allow you to highlight a section of text which you have to type in order to pass the card. They are much more effective than regular flash cards, especially for foreign languages (or anything that requires accurate spelling or precision typing, e.g. code syntax.)
See the Cloze Deletion section: https://docs.ankiweb.net/editing.html
2. Try to make the cards into real-world examples. For instance, don't add the conjugation table, create example sentences for each of the conjugations and make each one a card. For foreign languages, I try to add audio to my flashcards, too.
3. Always make your own cards. Downloading premade decks never works and you miss part of the learning process.
4. For things that don't necessarily lend themselves to being on a flashcard, don't just write the information. Try to frame it in terms of a question and/or in a form that mimics the context in which you'd use the information.
For example, let's say you want to memorize the periodic table. Don't just write:
Carbon - Atomic Number: 6, Chemical Symbol: C, etc.
Instead, create cards with questions like:
What is the sixth element on the periodic table?, Is carbon before or after nitrogen?, What element has the chemical symbol C? and so on.
The more "viewpoints" you have of the topic, the better. I've found this to be a solid approach for virtually any topic.