One of the way is to compare G and 2D band intensities- for graphene 2D band is much higher than G. The other way is to observe and calculate FWHM of 2D band. For graphene 2D band is sharp single line, for more layer 2D band become wider.

All is presented in Ferrari at al. Phys. Rev. Lett. 97, 187401 (2006) . In this article is also shown the difference between graphene and graphite.

I found this one time on the internet. It is a slide from a presentation refering to the publication of Ferrari et al.

I think that integrating the Raman with the SEM is very helpfull in this case. If you are interested to learn more about that contact me at [email protected]