Maya - Zbrush Workflow (Goz)

Maya - Zbrush Workflow can easily happen with the plugin (in Zbrush 4 and up it is integrated) - called GOz. Even it gives you a great comfort of NOT importing/exporting .obj ..still there are some tricks and mistakes you can avoid if you know how.

When for the first time installed Zbrush finds your programs (Preferences> Goz) - you can see /click the paths to different programs (Cinema 4D, 3D Max, Maya, Modo). When its connected to Maya - it makes a separate shelf (mel) in Maya called GoZbrush - with only button there (GoZ). I have encountered a problem, one time that button disappeared for some reason - and I had to DELETE the shelf and re-install the path to Maya again.

In Maya you must select your low poly model and click Goz button, it will directly import it in Zbrush (if the program is not active it will open it for you).
Be careful as Zbrush does not like Nsided faces - that are NOT quads or triangles. It will give you a warning.
a) Zbrush can automatically convert those Nsided faces for you
b) You can check your model before exporting with Goz to Zbrush:
Select your model, go to faces mode. Click Select (on top menu) >> Select using Constrains..
Constrain: All and Next
Properties - Order - NSIDED (it will show all faces that need to be corrected).

Another thing to AVOID by all means. When you work on your model in Zbrush and lets say you have hidden part of your model with "drag while holding CTRL SHIFT".. IF at this moment you click Goz to export your model to Maya... there is a very big possibility for your model to be gone/ skrewed forever. So make saves often and make NEW files (like keeping good archive of the steps while modeling).

RESETTING the scene in Zbrush when importing models - (so to avoid  for Zbrush to try to re-topologize or "update" your old model).
If you are working on a model and at some point would like to import another one, >>>exit "edit" mode, press CTRL +N (for new scene), SELECT ZSPHERE (in th "Tool" menu) - that completely resets the scene.


LAYERS.
Having a couple of layers while working on your model is not a problem for exporting. The problem is if you have ACTIVE layer (on recording mode), so make sure you don't have a layer that is currently recording, and then export your model.

SYMMETRY (when pressing the X key you turn symmetry On and OFF)
There can be many problems with symmetry when working Maya-Zbrush. Always make sure the models you export from Maya (or Goz to Zbrush) are in the absolute center of the grid (for X if you want to work with X symmetry, and so on).
TIP1. If you have your model with different parts which is symmetrical in Maya, if when you use Goz to Zbrsuh the symmetry is OFF, TRY to Goz first the very symmetrical part of the mdoel, then import the rest.
TIP2.
Also in Maya - CUT the half of your symmertical body (faces, select the half and delete) - go to Vertex mode, select all verticles along the  try to snap the centered verticles along the Y grid Axes, hold X (for snap to grid), make sure in the Move tool options (in Tool settings, when you double click move tool it opens) - make sure "Retain component spacing" is OFF. Then go to Object model ,select the cut half - Mesh -> Mirror geometry (option box) choose between +X or -X (depending on which part you have deleted) and have "merge with the original" and " Merge vertices" ON.
Another good things to check:
 - Delete history in maya
 - Freeze transformation and Reset Transformation after that puts the pivot point in the absolute zero of the grid.
 - check UVs if you have any uv out of the square box area.
TIP3. another problem to research is if your mesh is WAY to big (gigantic) that can cause issues in zbrush.