The purpose of a contactprint, if you intent to enlarge, is to have a work print to start with. This means that you have to print a contact pure technically, it must not even look good. To do this, the enlarger settings have to be always the same (aperture, lens, height). You determine correct exposure by making test strips, going for a maximum black exposure (first strip where the black densitity does not increase anymore by adding exposure). You use always the same contrast filter (#2 or #|).