If its ok with the parents and the child is old enough draw a small happy face on each shoe, tell the child that the happy faces must give each other a hug/kiss when you put your shoes on. If the happy faces aren't facing each other then they are on the wrong feet. Worked for one of my daycare kiddos who just couldn't grasp the right feet
This is a cute idea too!
Children construct their own intelligence. The adult must provide activities and context, but most of all must be able to listen. Children need proof that adults believe in them. Their three great desires are to be listened to, to understand, and to demonstrate that they are exactly what we expect."