The following settings are recommended up to NX 11 and CATIA V4.2.5 with COM/STEP 4.3.1.0.

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.

CATIA V4 (T-Systems) - STEP Postprocessor

• The COM/STEP STEP processor can be used in batch, interactive and java mode. The following descriptions refer to the Java GUI.
• Menu CATIA:
  Set dimension of CATIA model to required values.
  INDEX and DATA size should always be set to generous values (50000, 200000, or rather (100000, 200000).
• Menu Conversion:
  Represent face identifier: NO
  Supporting surface of face into: NOSHOW
• The import log file gives further information.

CATIA V4 (T-Systems) – System

• Each component of an imported assembly is located in a separate workspace.
• The master workspace shows the whole assembly.
• To remove the text added to the model use: TEXT -> ERASE -> *FAC+*SUR etc.
• Shaded view is helpful for a first impression of model quality.
• With IDENTIFY look for received SOL, VOL or SKI.
• Use CATCLN.