Math talks are a great tool for any age. Math talks are a classroom discussion revolving around a specific math concept. These can be simple and easy or more complicated to prompt deeper thinking. One of my favorite images to do a math talk on comes from Prime Climb and is a 100s chart. I have seen this math talk done with 5th grade and it would be a great discussion for a middle school class as well. The point of math talks is to build a deeper understanding of math concepts and for students to problem solve.
Math manipulatives are a great tool, especially for a geometry class. When it comes to manipulatives in the classroom, there are some important things to think about. An article posted on Beyond the Worksheet titled "Math Manipulatives in the Middle School Math Classroom" talks about some things to do to include manipulatives in class. These tips are to choose the right manipulative, introduce the manipulatives, encourage exploration, use manipulatives to model problems, use manipulatives for group work, and use manipulatives for assessment. Doing this with manipulatives in the classroom will result in meaningful use of manipulatives and a growth in student learning and understanding.
There are many math games that can be played without students needing technology. Even if the game does not relate to the specific concept you are teaching, playing math games are a great way to engage your students in math in a low stake manner. One website that has many wonderful ideas is We Are Teachers. One of the games that stands out as a great game for middle school or high school is challenging card combo. One player picks a two digit number, other players choose four cards at random. Each player tries to use their four cards and any operation to get as close to the target number as possible.