The perimeter of any shape is the measure of all its sides. To determine the perimeter of any shape, you simply add the lengths of each of the shape's sides. Give students flexible tape measures and a variety of shapes and have them measure and record each shape's perimeter. Have the students measure each side separately and add them together as well as measuring the full perimeter to show that these measurements are equal. For circles, teach them how to calculate the perimeter by measuring the radius, then have them measure the perimeter with the tape measure to verify their calculations.
There are several books pertaining to geometry and shapes. Consider reading one or more of these books aloud to your class. Have your students create the shapes you're reading about on the chalkboard or using models. Many of these books are picture books that you can share with your students to show them common shapes.
Give your students rulers, some glue and yarn or string. Ask them to make a variety of shapes by gluing the yarn to a piece of construction paper. Give the students the perimeter measurement for each shape, or provide them the measurements of the individual sides and ask them to measure the yarn, cut it and create the shapes. Providing just the perimeter information allows you to demonstrate to your students that a variety of different lengths and widths can make up shapes with the same perimeter.
Take your students on a walk through your school's campus and have them identify as many shapes as they can. You can also ask them to do this at home. Have each child keep her own shape diary or journal and tell them to record each time they encounter a specific shape. Also have them write down what the object was. For example, if a student encountered a round wall clock, she would write down that she found a wall clock with a circular shape. A shape diary helps students see the geometry of the world around them.