Teach the basic geometrical shapes such as circle, square, triangle, rhombus, hexagon, rectangle, pentagon and octagon. Help the student understand that knowing the words can help remember what they are. For example, hex is the Greek word for six, therefore the hexagon has six sides. Math Is Fun has a website (mathisfun.com) with information about geometrical shapes that range in grade level, such as solid and plain geometrical shapes.
Provide worksheets that are grade level appropriate. For example, beginning geometry students would need basic shape worksheets that will help them to memorize such things as the name, spelling, and how many sides a shape has. Worksheets may be found on the Super Teacher website (superteacherworksheets.com).
Utilize online resources to embellish lesson plans. Once students had an opportunity to learn a concept find an appropriate website they may find games and play to help reinforce geometrical concepts. Home School Math (homeschoolmath.net) has free games that students can play to reinforce geometrical shapes.
Present geometric concepts by using relevant examples. For example, for the concept similar versus congruent, use the example of two rectangles of different sizes. Ask the question: "Are they similar or are they congruent?" The answer is that they are similar. They are the same shape, but they are not the same size. Another example would be a square that is 2 by 2 inches and another square that is 2 by 2 inches. They would be considered congruent because they are both the same size and the same shape. Study Zone (studyzone.org) has more examples you can use. The Lesson Plans Page (lessonsplanpage.com) has examples to help at the middle and high school levels.