(And know your tools)
Every exported models should have correct pivot placed on their center, with freezed position, rotation and scale. If, in any case, the 3D model imported is also available as single instance, the UV should be game-ready, divided by Props usage and percentage (%) of screen space.
You shouldn't have a Camera in your scene when building your files for Versy. So make sure to delete them. There are some situations where you may want to use a camera to override the Users experience, but initially it is recommended to delete any Cameras in the scene.
The first one that most builders come across is the polycount. This is how many polygons (or squares/triangles on a model) are used in a 3D asset. Any architect that uses Rhino or Revit will have not needed to worry about this (as both applications don't really have the tools to customise the result), but this is actually one of the most important elements for assets in the Metaverse.
Notice how when these assets are smoothed that it is mostly the edge that tells how low polygon it is. Use this as a guide for designing your assets.
The most important thing is to make sure that your assets do not look like the example on the left of the example above. This polycount is very high and will affect performance the more assets you have of this number (which should be zero), and it will also affect the filesize.
When it comes down to it you want to get the polycount as low as possible while keeping it as close to the quality that you would like (within reason). Depending on the asset you are creating there may, or may not, be compromises needed. Many straight or boxlike assets require less polygons than curved assets for example. So curved assets will usually need to use some game dev tricks to get similar results.
This is even more tricky when you have an asset that has a lot of detail such as a detailed sculpture, pillar, character etc. there are tricks to deal with these too.
Every asset requires different process to get the best result. Things to consider for which method is best include the following :
How big is the asset in the scene (how big will it get on the screen)
How important is the asset (is it a 'Hero' object like a main sculpture, or a vase in the corner no-one will look at)
How many of the asset will be in the space (is it placed once, or many times)
Once we have a good idea of the target asset, we can consider the materials and textures that it will use.
Materials are what gives an asset color and texture. More detail will be added below under the Textures section, but a material includes all types of information such as the color, metallic, smoothness, normal (or bump), emissiveness, to name but a few.