How to find and change material for certain faces? I have a mesh, which renders strangely.



I think the reason is that part of the mesh has a different material, than the neighbouring parts. I want to change this material. In total the mesh has about 12 materials showing up and it is hard to understand which one is which. Also, I don't find any vertex groups to select these particular vertices. 

How to find out which material is used by these vertices and change it to the material, that neighbouring vertices use?
Materials are assigned to faces.  

Enter edit mode;
change your selection mode to face mode; 
select the face of interest and its material should become highlighted in the material list.

To go the other way (figure out which faces are used by a material);
change your selection mode to face mode; 
deselect all faces; 
choose the material of interest; 
use the Select button beneath the material list (which only appears in edit mode) to select those faces.