First, you ask your neighbor to come over and tell him
"here, hold the tip of this plug wire while I crank it." If he screams and jumps when you crank it, then you have spark.
If you have no spark, then you manually test the MSD unit by first physically closing and opening the connection by jumping the wire leads to the pickup. if that fails, then the problem is upstream at the MSD box or coil. If you get spark by shorting the wires, then you know it's downstream at the distributor. A "no spark" condition is very easy to diagnose. An "intermittent" electrical misfire/dropped-spark/weak-spark condition can be a heckuva lot trickier.