when checking transistors on a circuit board with a DMM, unsolder the B and E leads and float them in the thru-holes. this eliminates false readings from other components in the circuit.
in stereo and multichannel amps, if you have a good channel, you can double check your measurements (voltages, etc in powered testing, and resistance readings across components in unpowered testing) against the known good channel. sometimes the channels are laid out identically, or mirror-imaged.
when powering up a suspected shorted amp, or powering up anything after any power supply or amp repairs, an incandescent bulb in series with the power line will act as a ballast resistor if something is drawing too much current. the nonlinear temperature vs resistance properties of the incandescent bulb will allow the device to operate normally if everything is ok, but will drop enough voltage if there is a problem to protect everything from further damage, as well as operate at reduced voltage and current long enough to do some troubleshooting. with audio amps, this test is done unloaded.. choose a wattage for the bulb of about 5-10 times the IDLE wattage of the device under test. the wattage of the bulb is correct for the unit under test, when with the unit idling, the bulb glows with a barely visible reddish orange glow. the initial inrush current of power supply capacitors will light the bulb up bright, but it should dim down within a short time (usually 5-10 seconds or less).
when troubleshooting an audio amplifier, you can in most cases replace the output transistors with 1500 ohm/2watt resistors across the B-E connections. this will close the feedback loop and allow the amp circuitry(before the outputs) to operate normally. never attach a speaker or dummy load to the amp when it's in this condition, this is only for checking voltages and waveforms. shorted drivers will smoke these resistors in some cases. with the feedback loop closed, you can troubleshoot many offset and gross distortion problems, as well as bias circuit problems, etc... one amp manufacturer i worked for, used a pair of TO-3 transistors with the top cut off, the B-E bond wires removed, and the 1500 ohm resistors soldered across the B-E posts, so we could troubleshoot an amp without removing the PC board from the heat sink, and without the danger of ruining a pair of new output transistors (resistor $0.20, power transistor $10.00).