  In relativistic heavy-ion collisions, properties of the initial state and
effects arising during evolution of the medium, such as a transition between
the hadronic and partonic phases, should reflect themselves in event-by-event
fluctuations of the number of produced particles. In this paper, recent
measurements of several event-by-event observables, namely, dynamical
fluctuations of relative particle yields and forward-backward correlations of
different types, are discussed. Also, new observables for forward-backward
correlation studies are proposed: correlations between ratios of identified
particle yields in two separated acceptance intervals and the correlation
between the ratio in one interval and average transverse momentum in another.
