I modelled a dinosaur and then I wanted to sculpt it, so i set a multiresolution modifier and smooth shading, but some places have strange shading. 
There is odd shading on the mouth and paw (hand). I recalculated normals, checked wireframe, but I didn't find anything. Can someone help me?
The shading artifacts are due to bad normals direction at random faces. Go to your model, enter edit mode, press "a" to select everything, press space and write "make normals consistent" (or press Ctrl+N). Remove the old "multiresolution modifier" and add a new one. I've just noticed, your normals were inconsistent already from your low poly model.
The smooth shading is probably trying to force Blender to smooth out vertics that can't be smoothed due to the complicated shape. I can see that the top of the snout is clearly a very complicated part of the model, so parts that can't and/or shouldn't be smoothed are being smoothed anyway. To solve this, try messing around with the details of the model, or separate that part of the dinosaur from the rest as a separate model, and parent it to the original. Just don't smooth it. :)
