You need to recognize that even though some people are not required for a decision to be taken (see Prepare the agenda), many need to be informed of what took place during the meeting in question.
This is a very common mistake made in organizations throughout the world. Communicating the results of the meeting to a larger group increases the chances of receiving feedback that questions the decisions. As a result, people tend not to communicate in order to avoid having to answer comments or worse, having to rework the whole decision.
The earlier you communicate on decisions taken, the less such last-minute feedback you will receive. It will also push people who want to take part in the decision making process to get involved early.
If you have been transparent early on and nobody manifested interest or concern, it is easier to “discard” their last minute comment if you feel that are not justified. One way to go about it is to share the agenda with everybody who will eventually be notified of the decisions taken. This way they can contribute (ahead of the meeting) to the different topics without attending the meeting.
All in all, as an organizer, try to be mindful of people’s time and only invite the people who are required to solve the issue at hand. If you are unsure, make it clear in the description or directly reach out to the people who are unsure about the specifics of the meeting.
Finally, always share the meeting's summary with all the participants along with all the people who need to be made aware of the decisions even if they could not join or were not invited to the meeting.
When meeting with someone (often external to your company) such as a person from your ecosystem, an investor, a fellow entrepreneur or potential customer, three rules apply:
A simple thank you email can go a long way. It is also the occasion to emphasize the key takeaways but also to act upon the help the person offered, such as an introduction to someone, a document etc.
Do not wait more than 24 hours for following up and do not hesitate to follow up once more 3-4 days or a week later in case the email fell through the cracks. Most email clients have a Snooze functionality that can be used for that.