Here are some ideas and tips that I hope, could be useful in your situation:
1. I think that it is important to vary your activities. If the grammar exercises have always the same format (ex. Filling the blanks) students can get bored. So, it’s better to vary the types of activities.
2. When you choose your activities, you could try to make them more related to the students’ interests. For example if you use an exercise where students need to write down the sentences in the appropriate tense, change the sentences so that they would be related to themselves. They could be about the new film that is on in theatres, or about the heroes of their favourite comics or tv series. Adapt cultural context (if this is the case) to the cultural and personal background of your students. Make them feel that this is interesting and useful information that is related to the real life.
3. Promote interactional and cooperative learning. Example. Divide the class in groups of four. Distribute cards. Each student will have one card with one, two or more verb (pronoun, preposition etc, depending on the grammar material) written on it. Each student needs to have different words form their team mates. Ask student to write a story. Explain them the procedure. Student A writes the first sentences, using one verb from his/her card, then it’s Student B’s turn etc. At the end they will have a story written together with the use of the grammar material. While they are doing this activity, they will use English, different sources (dictionary, peer help etc). These types of activities are challenging, interesting and funny.
4. Use IT, media support. There are a lot of activities (most of them are free) that you can find on-line. Songs, clips, games, crosswords, quizzes etc.
5. Give students choices. Some students could have difficulties with some types of exercises or they could feel more ease with different types of exercise. So, make them choose. Ex. They can choose the order of the exercises to do. Ex.2. when they finish their exercise, tell them that they can do another one, more challenging, for some bonus points. Ex.3. they can choose between retelling a story you’ve read and telling their own story using the 5-10 key words form the story you’ve read.
6. Use active learning. Make them participate in their own learning. Ex. Instead of giving students the text with the questions that they need to answer, ask students to read a story, and make them write down questions that their peers will need to answer. Ex.2 if it’s a reading activity, ask students to bring their story book from home that you’ll base your reading activity on. Ex.3, ask students to create a grammar crossword. Ex.4. call on randomly on some students and ask them to explain the grammar rule to the class.
7. Use their creativity. If your topic is about travelling (food, music, sport etc.), ask them to create a poster. And to present it to the class.
I wish you good luck with your students:)