  We calculate cumulants of fluctuations of net-baryon number, net-electric
charge and net-strangeness, in the framework of lattice regularized QCD. We use
a highly improved staggered quark (HISQ) action on lattices with temporal
extent of N_tau=6,8 and 12 and almost physical quark masses. By means of a
Taylor expansion in various chemical potentials and under demanding both
strangeness neutrality as well as the correct isospin asymmetry, we evaluate
these fluctuations at conditions met in heavy ion collisions. Cumulants of
net-electric charge fluctuations can, in principle, also be measured in heavy
ion experiments. We therefore propose a method to extract freeze-out
parameters, such as the freeze-out temperature and baryon chemical potential,
based on a comparison of lattice results and experimental measurements of two
different ratios of net-electric charge cumulants. As this method involves only
(lattice) QCD results and experimental measurements it is model independent
and, for the purpose of extracting freeze-out parameters, does not require any
input from hadron resonance gas model calculations.
