I hope this does not sound too traditional, but I find that the old-fashioned technique of giving students sentences to translate from English into French targeting a specific grammar concept (like relative pronouns qui and que) usually works wonders for instilling a concept in their minds. The hand/writing/mind connection is great for learning a foreign language. Besides, all French students should have an understanding of grammar in case they want to move on to higher levels. When practicing a specific grammar point, I explain and share my understanding of the concept and then allow a few minutes for it to soak in and for the student(s) to ask any questions they have. Then, we usually work on exercises from their textbook relating to the concept under study. I also like to ask the students what they feel they need help with, and then I come up with with examples for them to work/write out. For instance, if a student is struggling to understand the conditional tense, I play a game with them where I say one verb in the infinitive and require them to write out all forms of the verb in the conditional. I'd repeat with different verbs at least two more times.