When dealing with meetings a good question to ask yourself is what is your role in it? Are you the leader or are you just providing your boss's availability?
If you are organizing the meeting, then you are responsible to send the initial email out requesting the participants to attend. You will need to give them as much information as possible so they can make an informed decision about attending. If you know their assistant's email address, I always copy them on this initial request. If you don't have their email address, many bosses will copy their assistants when they reply to the initial request and you should keep a note of that and include them in any follow up emails.
The people invited need to know the purpose of the meeting, you should provide three or four dates and times for the meeting, they need to know who is calling the meeting and why their attendance is needed. Once a date is agreed upon, you will need to book the meeting room, confirm the details with the participants, make sure they have the materials they will need and if the meeting is cancelled, you need to make sure you undo all of the above and cancel the room, notify the participants, re-schedule if necessary, etc. You are the leader in this type of meeting.
If your boss is to be a participant in a meeting then your role is less involved, but you need to follow up nonetheless. If you receive an email for a meeting request, but it doesn't have any information about the purpose of the meeting or information about whether it will be a teleconference or provide the location and time, then those would be good questions to go back with. Once you have all the information, you need to bring it to your boss and ask him or her if they need to attend. If they do then you need to provide the meeting organizer with the times your boss is available and if it is out of town and your boss will not be in that city, you can ask if your boss is able to participate by teleconference and what are the call-in numbers? Once the meeting is organized you should make a note and diarize it a few days before the meeting to follow up to make sure the meeting is still on and that you have received all the materials needed (agenda, background materials, etc.).
Sometimes your boss will send you an email request for a meeting that they received in their Inbox and ask you to get back to the meeting organizer with his or her available times. In this case, you know right away they want to attend, all you need to do is provide their availability and get any information you are missing such as the location, time and whether it is in person or by teleconference. If the purpose is vague, I usually go back and ask that as well. If you manage your boss's Inbox then one of your roles when you find emails such as this is to ask them if they want to attend and if they would like you to get back to the meeting organizer with their availability and then take it from there.
In my organization we deal with government and many times we will get a request for a meeting with my boss and ask for his availability. I will first check with him to make sure he needs to be at the meeting and if anyone else from our organization needs to attend with him. Once I have all the information then I can get back to the person requesting the meeting to give available times, request the agenda and meeting materials and give the names of the people from our organization who will be attending. My role then becomes the leader, at least as far as internal participants are concerned. I will be the one who needs to make sure to pass along the meeting materials to them and ensure they have all the details about the meeting and if the meeting is cancelled to make sure to notify everyone. You should also ask your boss if a pre-meeting will be needed as oftentimes if they are meeting with the government they want to make sure they are prepared and have all the information they think they are going to need. You will be the one who will have to organize that meeting.
If you know your role in the meeting then it makes it easier to determine what your next steps need to be. If you are ever unsure -- ask! Never be afraid to ask questions.