Nano indentation test to characterize the mechanical behavior of materials

[pav93]

I will have to do nano indentation tests to study the mechanical properties of a few specimens that are coated with same or different material as that of the substrate. I would like to know on what basis and how to choose the indentation load, the loading rate and any other parameter data required prior to the testing? Also would like to know when and why do we go for a constant load (profile nano indentation) and a variable load indentation?