  We discuss and propose a complete data treatment, in close contact to typical
microwave experimental data, in order to derive vortex parameters, such as
pinning constant and viscous drag coefficient (also referred to as ``vortex
viscosity''), in a way as model-independent as possible. We show that many of
the accepted models for the complex resistivity can be described by a single,
very general analytical expression. Using typical measurements of real and
imaginary resistivity as a function of the applied field, we show that, even
for single-frequency measurements, it is always possible to obtain (a)
estimates of viscous drag coefficient and pinning constant with well-defined
upper and lower bounds and (b) quantitative information about thermal creep. It
turns out that neglecting thermal creep, in particular and counterintuitively
at low temperatures, might result in a severe overestimation of the viscous
drag coefficient. We also discuss the impact of thermal creep on the
determination of the pinning constant. The present results might lead to a
reconsideration of several estimates of the vortex parameters.
