The following settings are recommended up to NX 11 and Autodesk Inventor 2017.

NX – System

• Delete blanked elements before preprocessing.
• To transfer colors of assemblies the colors should be set and saved with the individual components, not the assembly.
• Note that NX uses the radius of a "tolerance tube", other CAD Systems like CATIA V4 define "tolerance" as the distance between two points.
• Select Analysis -> Examine Geometry -> all options -> all elements (up to NX2). 
• Select Analysis -> examine Geometry -> Set All Checks (up to NX8.5) The marked elements are likely to cause problems with data exchange, depending on the messages as explained below:
• Severe errors:
  data structures, consistency, face-face intersections, self-intersections
• Might cause problems:
  tiny, face smoothness, spikes/cuts, edge tolerances
• Without negative influence on data exchange:
  misaligned, sheet boundaries, edge smoothness

NX - STEP Preprocessor

• Start the external STEP processor with File -> Export -> STEP214.
• Select Data to Export and define the options:
• Object Types: One or more of the options Solid, Product Data, Surface, and Wireframe (depending on model).
• The default tolerance value in menu Advanced -> Parameters -> B-Spline Aprx. Tol. of 1.01*10-5 mm can cause to very large STEP files and should be reduced in such cases(recommended value: 10-3 mm).
• Recommended is to use the default settings in menu Translation Control (Tolerant Modeling).
• Special characters in the filename of the STEP file are not allowed. The model will not be exported.
• Validation properties are supported.

STEP File

• No adjustment is necessary.

Inventor - STEP Postprocessor

• To import a STEP File please choose File -> Open... and select STEP file.
• It is recommended to import the STEP files first without any automatic healing (in options selectable).
• The import log file "filename.xli" gives further information.

Inventor – System

• Shaded view is helpful and gives a first impression of the model quality.
• A volume calculation of the imported model gives more information about a successful import of a solid.