Layering: example 1
Pour the liquor slowly over the back of a spoon, touching the side of the glass. This (hopefully) allows the liquor to trickle into the drink without too much downward disturbance, and settle nicely upon the top of the previous layer.

Layering: example 2
Pour the liquor into a glass. Tilt the glass to a 45-degree angle and slowly pour the next layer down the side of the glass so that it floats on the first layer. Repeat this procedure for following layers.

Layering: example 3
Add juice/liqueur in a rocks glass. Take a napkin and put it over the glass pushing it down toward the juice. Push the napkin down as far as it can go without touching the juice. Next pour the liquor very slowly so it dribbles on top of the 1st layer. This will create a layer of liquor that lies on top of the juice because of the different densities of the liquids.