Let's say you're playing with this sentence/conversation:

1-Pour aller à la gare de Lyon, s'il vous plaît ? 

    - Prenez le métro, c'est à 2 stations.

Now, if you don't know the word "gare" already, then yes, you can absolutely use this to learn it.

 1-Pour aller à __ de Lyon, s'il vous plaît ? 

    - Prenez le métro, c'est à 2 stations.

(Add picture of train station)

Same thing for "Pour"

 1- __ aller à la gare de Lyon, s'il vous plaît ? 

    - Prenez le métro, c'est à 2 stations.

(Add picture of anything related to this scenario [trains, 2 people conversing, the city of Lyon, whatever])

The next step is to keep going, until you've covered all of the unfamiliar territory in this little conversation. If you're just starting out, "à" might be new to you. So you'd do the same thing with that preposition.

Also "prenez" is probably new. You might know "prendre" (to take), but you might not know "vous prenez". So you can do this:

 1-Pour aller à la gare de Lyon, s'il vous plaît ? 

    - __ (prendre) le métro, c'est à 2 stations.

That's a 'word form' card, where you're connecting a new word form to a base form that you know already.

You can do that type of card whenever you see a new word form that you haven't encountered yet (for verb conjugations, but also for plurals, adjectives, etc)

Basically, your job is to take a sentence or conversation where you understand what's happening, and then create as many flashcards as it takes for you to memorize all the surprising content. 

If something is already obvious to you, then don't make flashcards. But if it makes you go "Huh! That's interesting how they say that!" then make flashcards for that concept.

The third type of card is going to be a word order card, which you won't use as often as the other two card types (new words, like "gare" or word forms like "prenez") in French, but will still be useful. 

I can see a couple of potential uses here:

Le train de 8 heures pour Nantes part de Montparnasse ? 

     -Oui, c'est bien ça

It may be surprising that it's "Le train de 8 heures pour Nantes part de Montparnasse ? ", rather than "Le train pour Nantes de 8 heures part de Montparnasse ?" or "Le train pour Nantes part de Montparnasse de 8 heures? "

If that's surprising, then you'd make a word order card:

Le train pour Nantes part de Montparnasse ? (de 8 heures)

     -Oui, c'est bien ça

(And if the order there isn't surprising, then don't make that card.)

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