If there is no published star, or the aircraft does not have a star in it's database there are still ways that a pilot can navigate to an instrument approach.
In this case, the ILS/Localizer/VOR approaches will generally have what is known as a procedure turn, which will be defined on the approach plate. This is a maneuver from a known fix, usually a VOR located on or very near an airport. The plane flies to this fix and then outbound on a radial to a certain distance, then turns to intercept the inbound ILS/Localizer/VOR course.
While some procedure turns are in the navigation database, they can also be flown manually without much difficulty. Typically if there are radar services available, the aircraft will just be vectored to the final approach course, however in a lost comms or non radar environment, a procedure turn will substitute for a standard arrival.