The phase diagram of QCD in the temperature – baryon chemical potential plane has been a subject of intensified theoretical interest recently. On the experimental front, with the advent of large acceptance detectors such as NA49 and WA98 at CERN SPS, we are now able to measure average eventby-event quantities which carry information about thermodynamic properties of the system at freeze-out. Our goal is to understand what we can learn about the phase diagram of QCD from this newly available and future data. The main focus of our analysis in 1 is on providing tools for locating the critical point E on the phase diagram of QCD (Fig. 1) and studying its properties. The possible existence of such a point, as an endpoint of the first order transition separating quark-gluon plasma from hadron matter, and its universal critical properties have been pointed out recently in . In a previous letter, we have laid out the basic ideas for finding this endpoint 4 in heavy ion collision experiments. The signatures proposed in 4 are based on the fact that such a point is a genuine thermodynamic singularity at which susceptibilities diverge and the order parameter fluctuates on long wavelengths. The resulting signatures all share one common property: they are nonmonotonic as a function of an experimentally varied parameter such as the collision energy, centrality, rapidity or ion size.