What ensures that the salespeople follow up with customers?

Follow-up rarely falls through because someone is unwilling. It falls through because the next step was never decided.

The rule that works

Every active sales opportunity should have one open task with a due date. If it does not, the deal is effectively on hold. This is easier to follow up on than measuring activity levels.

Make the gap visible

Create a view that shows active sales opportunities without an open task. Spending ten minutes a week on that list will catch most of what would otherwise fall through the cracks.

Don't automate everything

Reminders for everything create notifications that people dismiss. One notification that matters beats twenty that don’t.