WPI LIB Guide
This guide will take you step by step through wiring an FRC robot from start to finish: https://wpilib.screenstepslive.com/s/currentCS/m/cs_hardware/l/144971-wiring-the-frc-control-system
General Best Practices
No whiskers. When using push to connect fittings make sure the wire is stripped to the correct length and has been twisted together so there are no "whiskers" that could cause a short.
Crimps > Soldering. Soldering wire introduces difficult to identify points of failure. Crimps/connectors should be used when possible.
Components should be modular. It should be easy to swap anything from a motor to a motor controller to the PCM with basic hand tools in less than 2 minutes.
Thin wires need to go in sleeving. Anything 20AWG and under should go in sleeving.
Don't zip tie too tight! Wires can be cut by a zip-tie very easily. Velcro cable ties should be preferred.
Don't pull too tight! Wires should have proper strain relief, and should never be pulled tight.
Zip-tie Powerpoles, use clips on CAN. All connectors should be zip-tied or clipped together so they can't come loose. This includes a battery "oh-shit strap" which is a zip tie connecting the battery connector to the PDP/breaker connector so that if the battery falls outside the robot the robot is still powered and drive-able.