Hi ,
As with all graphic styles, there is never going to be a one size fits all tutorial, but for learning stylized graphics a couple of good places to start is to look at the Stylized Rendering content example, available on the Launcher, under the Learn Tab (documentation is here: https://docs.unrealengine.com/latest/INT/Resources/Showcases/Stylized/index.html?utm_source=launcher&utm_medium=ue&utm_campaign=uelearn
It’s a good place to go in and see how the materials, lights, etc are set-up and to fiddle with the settings to see how it changes the effects.
If you are looking for a more cel-shaded look, there is a great forum thread here: https://forums.unrealengine.com/showthread.php?306-trying-to-make-Toon-Shader-Material-on-UE4 which shows several developers working through their different approaches to cel-shading.
Hope this helps!