Always send the agenda before the meeting
Attendees can't prepare for a meeting if they don't know what to expect in it. If attendees are coming to your meeting without preparing for it, this hurts the quality of the group's discussions and decisions.
You created an agenda, but you plan to hand it out at the meeting rather than send it a day before
Attendees don't know what's on the agenda, so they can't think about the topics before meeting
Attendees have to react to each topic on the fly, making it hard to reach the best decision
When you send the agenda to attendees before the meeting, it gives them a chance to think through any topics that are applicable to them. By thinking about the topics before discussing them, attendees come to the meeting prepared to participate.
Put yourself in your attendees' position
Imagine that you'll be giving a presentation, but you won't know what the topic is until moments before. Since you won't have any time to prepare in advance, you'll be forced to collect and share your thoughts while you're still digesting the topic.
The presentation would be difficult and inefficient. You might ramble about something unrelated, completely forget an important point, and ultimately arrive at the wrong conclusion. None of these things would happen if you had only known about the topic a day or two before.
When attendees don't get the agenda before the meeting, they need to immediately participate in the discussion without getting a chance to prepare. It's just like giving a presentation without knowing what the topic is.
When should you send your agenda?
The last step in creating your agenda is sending it out to attendees. Try to send it to them 1 day before the meeting.
If you give attendees less than 1 day, they might not have time in their schedule to review the agenda before the meeting. If you give them more than 1 day, there's less urgency for them to review the agenda, and it might get postponed and forgotten.