Removing Knob and Tube
Removing lath and plaster wall to get at old wiring
The service comes from a pole in the alley or the yard and enters the house terminating in a fuse block with usually only one or two fuses that protect the whole house. Total electrical supply may be only 30-40 Amps vs today's 100 - 300 Amp service.
First, let's confirm we have knob and tube wiring and it is in service. Follow wiring to outlets and remove the covers. If you see solid copper wire covered with black or brown cloth insulation, you likely have knob and tube. Now go into the attic and, being careful not to step on wires, remove some of the loose insulation and look for parallel runs of wires passing through ceramic tubes. Yep, knob and tube.
It's quite likely at this point you will find that the entire system will need upgrading. You may have an electrical main panel that still has glass screw-in fuses. The main shut off may be a blade breaker. The entire system may be only rated for 50-70 amps.
If your insurance company doesn't know about this situation already, they will be very encouraging about this upgrade. If you are considering selling the house, it will be a mandatory condition that the service in the house be brought up to 100 Amp minimum. The buyer in fact will probably be unable to complete the deal without this upgrade being in place.
At this point it will become clear that even the wire from the pole in the alley to the house is not up to standard. The town or city will have to be involved, service to the house will be completely disconnected and a new drop of supply wire will be installed by the utility company.
Your electrician will find a location for the new main panel. This will be near the old one, perhaps right beside or replacing it entirely. It may also be in a new location depending on the connection point for the upgraded service from the alley.