First there is the hand support method. Place your elbow on the desk. Rest your cheek on that arm's hand. Angle your face in a way that it looks like you are paying attention to whatever is going on. Relax and daydream.
Next is the double hand support method. Place both elbows on the desk. Now you can either clasp your hands together or make a fist with both hands and lean them together. Now rest your chin on your hands and face forward. Daydream away.
Another great method is the I'm reading method. To do this you open your book or notebook and act like you are reading. You may lay the book flat on the desk or hold it in a position in front of you. Find a comfortable position and daydream.
The easiest way to daydream is the rest method. For this method you arrange your arms to make a little nest for your head to lie on. Scoot your chair back and rest your head on your arms looking either to the right or left. Enjoy.