Ride-alongs that teach something

A ride-along teaches when the experienced rep observes and lets the new one work, then debriefs on specifics immediately afterwards. It teaches nothing when the senior rep takes over at the first difficulty, which is the most common failure and the most tempting one.

Watching beats demonstrating, after the first hour

Seeing a competent rep work is valuable once. After that the learning comes from the new rep doing it badly with somebody watching who can say precisely what happened.

Do not rescue the door

Stepping in converts a lesson into a sale. That is a bad trade at training time, and it teaches the new rep that difficulty is somebody else's problem.

Debrief on specifics, immediately

One or two concrete observations right after the door. General feedback at the end of the day is about a conversation both people now remember differently.

Common questions

Who should knock during a ride-along?
The new rep, after the first hour of watching. Learning comes from doing it observed.
Should the senior rep step in?
Rarely. It wins a door and costs the lesson, and it teaches that difficulty gets handed off.
How long should a ride-along last?
Long enough for several conversations to go wrong. One good door teaches less than three awkward ones.