Howdy from Texas!

I'm installing a Harbor Breeze ceiling fan & am ready to wire.
I live in an old garage apartment and have 2 thick, single-strand, uncolored wires protruding from the box where I removed the previous ceiling fan from.

How do I tell which is the hot, positive wire and which is the negative (ground?) wire? I do have a multi meter & I suspect that it is as easy as checking the continuity of each wire with the power on. Whichever wire registers voltage or is the hot wire (positive) and the ground wire should not register any voltage. Is this correct?

Once I figure out which wire is which I'll be ready to wire up my fan/light fixture. I might have further wiring installation questions but I see that this topic is covered well here.

Thanks in advance!

Ricky

First it is hot and neutral, not positive and negative.

Look again, the wires are colored. It may be hard to see due to age.
If you truly cannot determine color;

If the box is grounded check for voltage between the box and the wires. If you get no voltage between the box and either wire the box is not grounded.

If the box is not grounded

Turn power OFF.
Remove switch.
Set the switch to ON position.
Connect a jumper wire to one of the wires in the ceiling.
Set meter to resistance. That's the little horse shoe setting.
Check for continuity between the jumper wire and one of the switch screws. The wire that has no, or very little, resistance is the hot wire.

Note: You do not check for continuity with power on. Be sure power is OFF, you will blow your meter if there is power when meter is set to resistance.

I'll say, at risk of pissing a lot of people off, (especially if the box isn't grounded) it doesn't really matter that much. Ceiling fans usually aren't polarized. Hook white to one wire, black and blue to the other.

Ceiling Fan Wiring - Ceiling Fans N More

CFR
That doesn't bother me.