How to hold people accountable for Action Items/decisions from meetings?

Sometimes people forget to follow up on their Action Items from meetings. They sometimes misremember meeting decisions as well. To mitigate this, I usually take detailed meeting notes in Google Docs and tag people on the Action Items they're responsible for. However, we don't always have meeting notes (e.g., for an ad hoc situation). What are some best practices for avoiding misunderstandings?