Use an interactive whiteboard to engage your students. Utilize some of the manipulatives available from the National Library of Virtual Manipulatives (NLVM), including sets of fractals, pattern blocks, pinwheel tiling, platonic solids and more. Using such resources will encourage your students to come to the front of the classroom and visually and physically engage with the stimuli on the interactive whiteboard. Choose different students to come up each time.
Group your students based on their abilities and assign each group a project from a tier appropriate to their skill level. For example, you could have the students who are most advanced do a research project based on a geometric concept, while you ask the students who are the least advanced to make scale drawings of their desks or one of the items in the classroom. You can also construct math labs in the same manner.
Your school may have a math fair that your students can participate in or you can set one up in your own classroom. Have your students work individually or in groups on a project chosen with some guidance from you. Some students may want to construct scale models of their homes, while others may choose to compare the angles of triangles in different sized structures. Have all of the students present their projects to the rest of the class.
You do not have to return to conventional methods when it comes to assessing learning in geometry. For example, you can assign brief quizzes every few days, listen in on your students' group work to see if they are using the correct terminology and/or have them fill out self-assessment forms. Ask your students to anonymously list the areas where they struggle the most so you can target these specific issues and problems.