In order to conduct a successful simulation of wireless ad hoc networks and in particular VANETs, appropriate mobility models should be included and applied in the simulation. This is important because mobility is the main feature of VANETs; it affects routing protocols, packet delivery and leads to communication and channel disruption. In this paper, main realistic mobility models are surveyed and categorized based on the approach used to construct the model. Couples of examples about each category were presented as well. The main aspects of realism in each model were highlighted in addition to their effects on network connectivity and performance. The paper aims at providing new researchers with an idea about the different methods and approaches available, to allow new proposed models to build their work on solid realistic models. This will help ensuring that the main features are incorporated in the model and will help in developing new approaches as well.