Recap Commitments

The last thing that happens in an interaction has a disproportionate influence on people's overall impression and memory of the experience (a consequence of the "recency bias," as it's known in psychology).

To help end on a high note, conclude calls, meetings, e-mails, and any other type of interaction with a recap of what specifically you're committing to do to help the person you're serving. This will instill confidence in your customer, showing them that you have everything under control.