Transistor Measurements

The transistor itself cannot do too much. First you need to select a configuration for your transistor. Let say that you've chosen a common emitter one, and the transistor is a NPN transistor.

Next, there must be a component, between the collector and a DC power source (at least 1V - the negative goes to ground and the positive to the other end of the component in the collector) that will have a certain impedance (to limit the current flowing into the transistor through the collector) and to signal the presence of the I or V that you are seeking. Such component could be the coil of a relay, a LED in series with a resistor, a buzzer... etc.

Now, for the third pin, the base. This is the one that, actually, will check the I or V. The transistor needs a small base current in order to control a larger current into its collector (it is necessary a limiting resistor in the base circuit, too). The place where you want to check the I or V must be referenced to the same ground as the emitter of your transistor. Also, the source of your base current must have such a voltage that there will be an approximately 0.7V between the base and emitter (ground). These measurements will draw a small current from your subject, and that might affect the measurement, itself.

This discussion is for a galvanic connection. A different way would be through induction but that would be a bit more complicated.

Use a multi-meter with current and voltage measuring capabilities.