Geologists call this the principle of lateral continuity.
A fossil will always be younger than fossils in the beds beneath it and this is called the principle of superposition.
This web page provides an overview of selected geochronology methods used by USGS scientists.
New dating methods are invented all the time, however, most have practical limitations.
Carbon-14 cannot be used to date biological artifacts of organisms that did not get their carbon dioxide from the air.