Paint on a sturdy surface; a normal canvas could sag under the weight of the wax and cause the material to crack and break off. A smooth plank of wood allows you to layer on wax without worrying about the integrity of the support.
You can prime the support using a few layers of encaustic wax directly on the wooden board. Many artists use a hair dryer to remelt the wax after it has been applied. This allows you to create an even coat for the background.
The nature of wax causes each layer of paint to be slightly translucent. You can use this to your advantage in several ways. You can layer different colors to create subtly shifting hues. You can also use this to seal in other mediums. For example, you can cut out an illustration of a tree and seal it into the painting with a layer of encaustic wax. This will create a multimedia look to your encaustic painting. Several layers of different colors of wax can be layered and then scraped away to reveal entirely different colors underneath.
You can also use the nature of the wax to create interesting textures and patterns by selectively melting sections of your painting. The focused heat of a blow drier can be used at an angle to cause the melting wax to drip and scatter across the painting in interesting ways. You can create a water effect by allowing the wax to melt and run down the painting vertically like droplets of water on a windowsill. Melted wax can be pushed around the painting with a painter's knife to create raised textures. This will create a mix of sculpture and painting in your piece.