Ask your students to show you their hands every morning when they come to class. Correct them if necessary and then stamp their right hand.
Walk up and down stairs on the right side if your school has stairs. Before reaching the stairwell, ask your students to raise their right hands because they will need to hold the railing with their right hands. Encourage them to try and do it without looking at their stamps.
Ask the children what letter "left" begins with. Show them that when they touch their thumbs together and point their fingers up that their pointer fingers and thumbs on one hand will make an "L" shape. Explain that the hand with the "L" shape is the left hand.
Play "The Hokey Pokey" -- a fun song with lyrics that focus on performing specific actions with the left and right hands and feet -- and do the dance with your students once a week.