Sometimes, the end of a meeting comes as a relief. You get up from your seat, file out of the conference room, and head back to your desk.

Chances are, you're thinking about the meeting you just left. But are you energized because you had a role in the meeting and know what you need to do to move the agenda forward? Or are you rolling your eyes because there's no way to get the last hour of your life back?

People leave meetings with very specific opinions of how they went.

And if you're the person holding the meeting, your preparation will determine whether people leave with a positive or negative opinion of the meeting they just sat through.

With the right planning, you can accomplish what you need to in a shorter amount of time, make people aware of their roles, and build trust in your process.

But to do that, you have to follow one simple rule: 

Spend as much time preparing for the meeting as you spend in the meeting.

If you're holding a 30-minute meeting, then you should spend at least 30 minutes preparing for it. There really aren't any exceptions to this rule. But that doesn't mean you only have to spend the exact length of the meeting in preparation. In some cases, your planning will take much longer.

If you're holding a weekly review, you don't need to spend several hours planning the agenda. But if you're presenting something to the founders of the company, you may want to spend a few days preparing.

For instance, when I worked at Aeropostale, I had to hold a one-hour meeting describing the impact of launching our company in an international market. I spent more than two months preparing for it. That's an extreme example, but it makes a key point. The more important the meeting, the longer you should spend preparing.

You should never shortchange your preparation time, even for low-stake meetings.

Part of preparation is inviting the right people.

It's very easy for meetings to gradually balloon in size.

We've actually run into this problem at ThirdLove. Sometimes, I look around and it feels like the size of our meetings has slowly crept upward until we've reached a number that just isn't efficient.

That's when you have to think about who absolutely needs to be at your meeting. If several people have their laptops open, checking their email and multi-tasking, then they probably don't need to be there. They can read the follow-up notes.

The point of a meeting is to educate people or drive a decision. If someone isn't necessary for accomplishing that task, don't invite them.

Once you have the right people, start with the 'so what.'

Preparation is great. So is telling people why they've taken time out of their day to come to your meeting.

You have to make people care, both in meetings and life in general. When you're standing at the head of a table and everyone's looking up at you, wondering why you've gathered them here, you have to be able to give them the "so what."

I was at a really good meeting the other day that was run by a woman on our team. She told us, "We all know the customer experience of returns and exchanges is incredibly important to us. It's not perfect, and we can make it better. The goal of today's meeting is to align around the next steps to update our exchange and returns form."

That was a great opening because it told the room why they were there and why they should care. The goal is to reach some sort of decision about the "so what" by the end of the meeting, even if it's just informing everyone of the next steps that need to be taken.

Always send a concise, helpful follow-up.

Every meeting has an owner. This is the person who sends the invite, does the research, and sets the agenda.

They've prepared, invited the right people, and kept everyone on track throughout the meeting. Afterward, they still have one more responsibility--sending a follow-up.

This is all about your ability to take good notes. If you can't run the meeting and take good notes at the same time, have someone take them for you.

Whatever the case, these notes should be distributed to every attendee. And at the top of the email, people should be able to see this: Here's what the meeting was about, here's what we decided, and here are the next steps.

Each task should be assigned to someone and have a due date attached to it. That way, everyone knows exactly who's responsible and when these next steps are going to be taken.

Adequately preparing and following through on your meeting shows people you care about their time, trust, and the topic you're covering. If you're going to treat your meeting lightly, then don't have it at all.