  Event-by-event fluctuations of global observables in relativistic heavy-ion
collisions are studied as probes for the QCD phase transition and as tools to
search for critical phenomena near the phase boundary. Dynamical fluctuations
in mean transverse momentum, identified particle ratios and conserved
quantities (such as net-charge, net-baryon) are expected to provide signatures
of a de-confined state of matter. Non-monotonic behavior in the higher-moments
of conserved quantities as a function of beam energy and collision centrality
are proposed as signatures of the QCD critical point. To study the QCD phase
transition and locate the critical point, the STAR experiment at RHIC has
collected a large amount of data for Au+Au collisions from $\sqrt{s_{NN}} =
7.7-200$~GeV in the RHIC Beam Energy Scan (BES) program. We present the recent
beam energy scan results on dynamical fluctuations of particle ratios and
two-particle transverse momentum correlations at mid-rapidity. Higher-moments
of the net-charge and net-proton multiplicity distributions as a function of
beam energy will be presented. We give a summary of what has been learnt so far
and future prospectives for the BES-II program.
