You need a "hi-impedance (10K ohms resistance), usually digital, volt meter. An ohmmeter can do some tests, but a volt meter is more useful. An ohmmeter need not be digital, and in fact, analog is preferable. A latching continuity tester can be even more useful, for finding dead spots.
The first thing to do is make sure you are getting 5 volts to the reference lead of the TPS, and that the ground circuit is good. On most cars, probing across the "A" and "C" terminals checks the positive feed and the ground at the same time. If not 5 volts, you need to test each terminal individually.
To test the sensor itself, you need to have it hooked up as normal, and either back-probe the wires, or use a 3-wire jumper (with exposed wires), to measure the return signal from the "B" terminal. You do this while slowly moving the throttle from one end to the other. This is called a "sweep test".
This is the test which can also be done with an ohmmeter. If you see the voltage drop to zero, or ohms go to infinity, you have a bad spot on the sensor. An ohmmeter would be hooked between the "A" and "B" terminals of the sensor itself, with the sensor unhooked. Ohmmeters are for use with circuits that have no power only.
A TPS is basically a variable resistor (rheostat), with more resistance at idle, to very little at Wide Open Throttle (WOT). Some also need to be adjusted at idle, to a very narrow range for the engines computer to know it's at idle. Some others incorporate an actual on/off type switch at idle and/or WOT.
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