Run through this general list of steps when encountering problems exporting models out from Blender 3D. Bottom line is to do as much of the work prepping the model beforehand
rather than relying on the export scripts to do the work because not all of them are set up the same way or will do the same 'autopilot' mesh preparations.
- Triangulate before export "Ctrl+T" (never rely on script to do that)
- Material + texture assignment
- Make sure there's a UVW map
- Split face/edge for smoothing where necessary "Y"
- Set POO before export
- Set rotation/position "Ctrl+A"
- Apply modifiers before export
- Select object (if more then one in the scene)
- Merge objects where necessary "Ctrl+J" (some export formats and scripts can only export 'single' objects - may also effect material assignment)
- Include collision where necessary [optional
- Break model up "P" [optional] (some exporters, model formats and/or game engines may have limitations in place)
- Make sure model is correct size
When exporting try and and use a minimal number of 'filters' as possible, or those that are used try and work out which ones are relative to 'low poly' work, for example when exporting and OBJ file the option to use "High Quality Normals" is usually useful for high polygon meshes used to bake normal maps; usually "Normals" is all that's needed for game content.Additional Reading
The following are links to useful resources for use when making content for use in games;