How your scene is laid out will have a big effect on much depth people will experience from the scene.
While our tools make it possible to do otherwise, when possible, keep the content of the scene inside the front of the physical Looking Glass. This helps create the most convincing illusion. Violating this (drawing content in front of the front glass) can induce depth confusion and can cause strain.
That said, short moments that violate this guideline can produce some dynamicism. Content can pop in front of the Looking Glass occasionally, but it should be for smaller objects that do not grab the main focus, and only for short periods of time.
The sphere on the left is too far forward and is perceptually confusing. The sphere on the left feels locked in place.
Content that lies on this plane looks most in focus. Consider what you're intending to focus your viewer's attention: the front face of your model, or the silhouette of the model? Placing the center of your main subject directly in the center of the Looking Glass puts the subjects silhouette in focus, blurring the front face. Try experimenting with pushing the model back inside the capture volume to sharpen the subject overall.
Anything drastically distant from the zero parallax plane will have more visual artifacts.
A common default choice beginners make when building for the Looking Glass is placing content in a black void. This tends to make the model feel disembodied.
Anchoring the content to a backdrop gives the subject a stronger sense of presence. Here are some guidelines for good backdrops:
Subtle textures will help the eye estimate the depth of the backdrop, whereas texture of a single flat color will appear to have an ambiguous depth.
Lighter backdrops catch shadows. Shadows play a big role in object presence and believability. More on this in the lighting guidelines.
Angled backdrops and backdrops which blend into the foreground (such as the inside of a room) help ground the main focus inside the Looking Glass and make the scene feel like an integrated cohesive whole. This is particularly true if the Holoplay Capture moves in the scene.