What do you want to export? - be aware of export scope e.g. meshes, cameras, lights, animation rigs, etc.
Applications often let you export selected objects or a whole scene.
Make sure you are exporting only the objects you want to use from your scene by either exporting selected, or removing unwanted data from your scene.
Good working practice often means keeping a working file with all lights, guides, control rigs etc. but only export the data you need with export selected, an export preset or even a custom scene exporter.
What do you need to include? - prepare your assets:
Meshes - Remove construction history, Nurbs, Nurms, Subdiv surfaces must be converted to polygons.
e.g. triangulate or quadrangulate.
Animation - Select the correct rig, check frame rate, animation length etc.
Blend Shapes / Morphing - Make sure your Blendshapes (Maya) or Morph targets (Max) are assigned / set up the export mesh appropriately.
Smoothing - Check if you want smoothing groups and/or smooth mesh.
Textures - Make sure to include/embed the textures/media in the export settings.
How do I include those elements? - check the FBX export settings
Be aware of your settings in the export dialogue so that you know what to expect and can match up the fbx settings In Modest3D - see figs 1, 2 below.
Check Animation / Deformations / Skins / Morphs as appropriate.
Cameras and Lights are not currently imported in to Modest3D but cameras and lights can be created and edited in Modest3D easily.
Which version of FBX are you using? use the Latest Version of FBX where possible.
Autodesk update their FBX installer regularly and it can provide different results with different versions of their own software and other 3rd party 3D apps.
See Advanced Options > FBX file format (Fig 2 Lights, Advanced options bottom of page).
If you have any issues you can revert to 2012.2 if necessary.
Will it work? - Verify your export
Check your file size - do a sanity check on the file size (e.g. >10kb?).
Re-import your FBX into a new scene in the 3D package you use to generate it - is it what you expected?
Modest3D standalone - place your exported FBX in the Modest3D standalone project folder (Project data) and run Modest3D
In the top right corner in the Assets window their is an Import Model button click it and it will take you to the project folder containing the FBX
Select the desired FBX and open.
Modest3D will convert the model from FBX to mtmodel (ModestTree Model)
Drag your mtmodel into the setup node and simulate