Stir frequently – maybe every 10 minutes or so. After 30 minutes, you will notice that the mixture has thickened. It will continue to thicken as it is cools. If you like your rice pudding thicker, then let it simmer a little longer before removing and placing into serving bowls. Also, if you want it a bit more creamy, adding more milk is the fix. Give it a taste test to make sure the rice has cooked, and has no bite to it.