A computational investigation of synthetic jet actuators operating in quiescent fluid is presented. The accuracy of low-level modeling, using oscillatory velocity conditions, is addressed by comparison with high-level modeling using moving membranes. The merits and drawbacks in each of the methods are discussed and several suggested guidelines for computational modeling, as well as performance prediction are provided. Vortex trajectories, jet formation conditions, averaged velocities, as well as instantaneous velocities are also presented in order to better understand the physical mechanisms responsible for the formation of synthetic jets. Computations are compared with experiment measurements acquired using PIV and hotwire.