Feed the track reliably
Do not assume rail joiners will provide perfect electrical conductivity forever. Larger layouts benefit from a power bus with feeder wires connected at regular intervals.
When a locomotive stalls
Check dirty wheels, dirty rail, loose rail joiners, turnout contact, and whether the locomotive stalls in the same location every time. Consistent location usually points to track or electrical trouble.
When cars derail
Check wheel gauge, coupler height, track joints, turnout points, abrupt curves, excessive speed, and vertical changes in the track. Fix the cause instead of accepting derailments as normal.
Finding shorts
Divide a layout into manageable electrical sections and test one area at a time. DCC circuit breakers and power districts can make larger layouts easier to diagnose.
A Simple Diagnostic Method
When something fails, change one variable at a time. If every locomotive stalls at the same spot, inspect that location. If only one locomotive stalls, inspect that locomotive.
Label wiring as the railroad grows. A few minutes spent labeling feeders and power districts can save hours later.