Vocabulary is one of the hardest things to "learn" for students, especially in a foreign language. Any given chapter that I teach, there are usually at least 50 new vocabulary words they have to learn. I'm not a huge fan of flashcards because I don't like my students memorizing translations. I want them to look at a pen and think "stylo". I don't want them to look at a pen, think "pen...pen in French is stylo...STYLO". Any flashcards I do use have photos instead of words.
One activity I love to do to reinforce vocabulary is a diagram project. For example, during the school unit, I had the students draw a diagram of the classroom and label at least 15 items (3 of which had to be verbs like raising your hand, talking, asking a question, studying, etc). It's a great way to apply vocabulary with them actually CREATING the vocabulary.