Help the preschoolers fold pieces of white construction paper in half to create a book's pages. Cut a piece of black construction paper in half to make the front and back covers, illustrating that "black" and "white" are opposites. Punch three holes in the side with a hole punch, then string yarn through to secure the book. The preschoolers can use chalk to decorate the front and back covers of the book. On each of the book's pages, have the students draw opposites, such as something fast, like a race car, on the left side, then something slow, like a snail, on the right side.
Give preschoolers activity pages that illustrate opposite concepts -- above and below, big and small, up and down, sad and happy. Many of these pages are available online at no charge. Another option is cutting out the opposites on these activity pages and creating a matching game for preschoolers. Spread the words or pictures on a table and ask the child to fit the pieces together to create an opposite.
Buy one or several wooden dowels, or use an empty paper towel tube. Tie a length of yarn to the end of the dowel. Glue or tie a strong magnet to the end of the yarn. The preschoolers use this as their "fishing rod." Cut out a five or more paper fish from various colors of construction paper. On one fish, write a word, such as "hot." On another fish, write that word's opposite, such as "cold." Attach two or three metal paper clips to each fish. Scatter the fish in the preschool classroom or find a small bucket, container or basket to hold them. Have the preschoolers "fish" for opposites. Students who catch an opposite pair win a small prize, such as a piece of candy.
Get preschoolers moving with a dance of opposites. Suggest opposite motions: kick your foot high, kick your foot low; jump to the front, jump to the back; clap your hands loudly, clap your hands softly; take a big step, take a little step; shake your hands fast, shake your hands slow and reach your hands up to the ceiling, reach down to the ground. Play children's music in the background to enhance the activity.