There are tones of useful tools out there that can help you in 3D sculpting. Some tools like Mesh Brushes or Nano Mashes are really hard to master and every time you use them feels like you are learning something new again. But I think the greatest tools are the ones you barely think about and using them feels as natural as breathing. One of these tools is MatCap! Actually you can find plenty of MatCaps online for free. ZBrush itself has a huge free library with great MatCaps. I, however, want to share 2 MatCaps by Michael Vicente, the Senior 3D Environment Artist at Blizzard Entertainment. These two MatCaps are actually just one material with (Orb_clay_gloss) and without (Orb_clay) glossy effect. On the image below you can see my sculpture with only one Orb_clay used as material next to the final coloured version.
It’s hard to explain why this material is so great. You cannot build any decent light with it but it’s the best from my opinion material to sculpt and to make intermediate renders. Once I started using it, I didn’t use any other materials in the process of sculpting. It shows all the cavities with the strong contrast, so you will never miss any mistakes and the final render will never surprise you with some ugly rough brush strokes you forgot to polish.
With these 2 MatCaps by Michael Vicente you will get a tutorial where he shows how to make the best renders with them. BTW Michael Vicente has some rad brushes as well!