Grammar review lessons are so important to help in the correction of fossilized errors and to clarify any misconceptions or confusions. At lower levels, students are often taught grammar topics in isolation without much of a sense of how the grammar is used in relation with other language points. One of the key lessons I learned as a new teacher was to take the grammar that students have previously learned and to teach them not only communicative but out of isolation.
One way to review grammar is to use sample sentences that the teacher hears them use regularly. This way the language is being taught in the most communicative way and the language begins to come alive to the students. They are also more likely to fix fossilized errors as they begin to notice the ones they commonly use as they are written down and analyzed.