Out begins by making you non-dominant hand into a cup. Then starting with your dominant hand, fingers touching and inside the cup, move your dominant hand's fingers from the starting position outside the cup.
You can make more specific signs for out, depending on what you are taking something out of. For example, taking something out of a drawer is signed by making a motion as if you were opening a drawer, then taking your dominant hand and bring it out of the imaginary drawer.
In and out are best taught together, as the opposites illustrate each other. You can demonstrate this by taking a favorite stuffed toy and placing them in and out of a box.
Out is used to show that you are removing something. The sign can be adapted depending on what you are taking something out of, whether it is out of a drawer or out of a cupboard. The flash card for em>out can be contrasted with the flash card for in.