We're doing work on our fixer upper, and so far I have found three instances where switches go to lights or sockets that we cannot determine.

It seems that two wall switches used to go to ceiling lights, there are two candelier type ceiling caps in the one room, so I'm guessing when I go into the attic to check them, that the switches will make at least one of those live. But in the other room, there doesn't seem to be any remaining evidence of a ceiling light. We tried to see if maybe it was connected to a wall socket, but it doesn't shut off any of them. We even check both top and bottom, since we used to live in a place where they were wired to only shut off the top socket in any given outlet.

The third switch used to belong to the oil burner which was removed during one of the additions and was replaced with a lp furnace which is now in a newer utility room. When I tested the switch, it is still live, but I have no idea what it is connected to, since turning it on or off doesn't seem to affect anything. (I even checked the new furnace, and that only seems to be connected to the switch next to it.) They drywalled over the chimney for the old furnace, and we're debating removing just the drywall or possibly even the entire chimney (but the latter is another post), in the hope that maybe we can find where the other end is.

I am a little concerned about not knowing where the ends of the wires are in these three situations, especially since two of the instanced involve either a dimmer or the types of switch that you just press at two places with no true on/off position, so we don't even know if they are "on" or not. There were several spots in the house when we moved in where fixtures were removed and they didn't even cap the wires, so I'm worried that they didn't cap them in this situation either.

Am I right in thinking this should be a priority in finding out where the end of the line is for these switches? Is there anything in particular I should keep in mind when trying to trace them? It seems that the furnace line had its own circuit, so it was easy to shut the breaker off, but the other two seem to share with outlets in the room from what little we've been able to interpret from the descriptions on the breaker box and trial and error checks.

Any advice would be appreciated.