Warnings:

Warnings in the Revit files should be as low as possible.

DWG links/imports:

Remove all Imported CADs from the revit Models including revit families too.

3D Views:

Delete unwanted 3d Views & Create a view with suitable visibility settings to be used as default view in CUBE.

Plans & Other views: Remove all unnecessary views from the file.

Model Size:

File size to be less than 500 MBs for faster conversion & smooth experience. You can Compact the Revit file from synchronisation settings.

Note: Heavier models may take time to get processed in CUBE. (Contact support if you face any difficulties in uploading the model)

Purge: Purge the Revit models at-least 3 times to remove the unused objects.

Model In-Place: Limit the use of in-place families