  Higher moments of distributions of net charge and baryon number in heavy-ion
collisions have been proposed as signals of fundamental QCD phase transitions.
In order to better understand background processes for these observables,
models are presented which enable one to gauge the effects of local charge
conservation, decays of resonances and clusters, Bose symmetrization, and
volume fluctuations. Monte Carlo methods for generating samplings of particles
consistent with local charge conservation are presented, and are followed by a
review of simple analytic models involving a single type of charge with a
constant experimental efficiency. The main model consists of thermal emission
superimposed onto a simple parameterization of collective flow, known as a
blast-wave, with emission being consistent with individual canonical ensembles.
The spatial extent of local charge conservation is parameterized by the size
and extent over which charge is conserved. The sensitivity of third and fourth
order moments, skewness and kurtosis, to these parameters, and to beam energy
and baryon density is explored. Comparisons with STAR data show that a
significant part of the observed non-Poissonian fluctuations in net-proton
fluctuations are explained by charge and baryon-number conservation, but that
measurements of the STAR collaboration for fluctuations of net electric charge
significantly differ from expectations of the models presented here.
