To check for short circuit, first disconnect the load(s) from the circuit. Loads are the components which draw current from a circuit, such as bulbs, motors, heating elements, etc.
Switch on the circuit, bearing in mind that some circuits are live only when the ignition switch is moved to a particular position.
If voltage is present (indicated by voltmeter) this means that here is a short circuit. Identify the short by tracing the wiring. Typical short circuits are due to damaged insulation where the power wire is touching ground (chassis).
If no voltage is present, but the fuse till blows with the load(s) connected, this indicates an internal fault in the load(s). Remove the component (load) and check for resistance in the component. Very low resistance would result in the component exceeding the current draw of the fuse rating. Compare resistance with a known working component.