Exporting from Blender to OBJ is quite straightforward and easy actually(because its not complicated format). Leave settings as they are because they are set for common situation. You need to know how OBJ handles shading(materials). OBJ file format contains mesh data that is assigned to material name. Besides OBJ file theres MTL file with more information about those material names. Each material can have values for Diffuse color, Specular color or texture map reference. So as you can see there is not much variations that obj material can have. OBJ is quite old and nobody even thought about using nodes to create complex materials like we have now in Cycles. If you want to export to OBj from Blender best work flow is to use Blender Internal and create material that way using only diffuse, specular and reflection. If you have Cycles material and that exported then bake that material to texture and again export with Blender Internal material which has that texture assigned as diffuse.
