  We present preliminary results for light, strange and charmed pseudoscalar
meson physics from simulations using four flavors of dynamical quarks with the
highly improved staggered quark (HISQ) action. These simulations include
lattice spacings ranging from 0.15 to 0.06 fm, and sea-quark masses both above
and at their physical value. The major results are charm meson decay constants
f_D, f_{D_s} and f_{D_s}/f_D and ratios of quark masses. This talk will focus
on our procedures for finding the decay constants on each ensemble, the
continuum extrapolation, and estimates of systematic error.
