I a have a lot of electric testers. I have one that looks like a screwdriver
Using a led bulb. It has a red and black probes. I know how to use it in an outlet.
But what about just a wire, how do you test the wires themselves to see if one of them is hot.
Do you take the probe on the wire and the other probe to ground?? To see if the bulb lights up.
Going to each separate wire.

Yes,


do you take the probe on the wire and the other probe to ground???? to see if the bulb lights up.
going to each separate wire.

Do you keep/read the instructions that come with all testers and meters?

Test instruments for electricity should not be used incorrectly.

Yes, it may be a neon bulb an will light if 1 probe(either), into the hot(small slot on an outlet and the other to neutral(large slot), you should also be able to show voltage when connected to a hot and a ground.
You can also test for voltage out of each breaker.
If you connect the probes to a hot and the other to a ground or neutral and it does not light, it does Not mean the hot is not live, you may not have a neutral or ground?
You can use an extension cord to use as a known good ground, then test for a hot.

Wonderful answer

Great comment