If it is a meeting with a client at their location, get there early. Just getting there 15 minutes ahead of time allows you be relaxed and be in the proper frame of mind to participate. It may also let you do the greetings and introductions up front in a more relaxed environment, which in turn lightens the mood and sets a positive tone for the meeting. It also gives you time in case there is a problem - and a problem could be as simple as you spilling something on your shirt and needing to purchase a stain remover. Or needing to go to the bathroom. Or drinking some water to compose yourself. 
If you are presenting, get there even earlier - perhaps allow for 20-30 minutes. Now the courteous thing to do is to let your host know that you will be there 30 minutes earlier to setup so they are aware and ready. You may need to hook up your laptop to the projector, setup the table/easel/find markers/distribute print outs etc. Imagine if you got there with only 5 minutes to spare, connected your laptop, and the cable doesn't work? You will start stressing out, and stress others out, leaving an overall bad impression and perhaps losing a client or at best, showcasing that you cannot manage your time. You may need time to find the IT guy to help you. As a side note, what's your backup plan?If the meeting is internal, some people are laxed about getting to it. People are fashionably late by 5-10-15-20 minutes. I have seen the meeting organizers handle this in many different ways - some close the door to the conference room and do not allow anyone else to come in after a 5 minute grace period. Others walk around frantically, looking for the missing participant(s), while some others ask to pay a penalty of $1 or something minimal as a token and acknowledgement for being late. Some others just sit in the conference room and wait... and wait... and wait. Is there a prescribed way to conduct a meeting? Ideally, everyone's there and the meeting starts on time, but that seldom happens.
I have personally tried all of the above with varied degrees of success. The most effective way I have experienced is to setup a reminder for the meeting in the invite (10 minutes works - 15 minutes is too long), and basically start on time. If someone comes late, do no recap the meeting and keep going. If someone is critical to the meeting and you want to make sure they are on time, check in with them 10 minutes prior so they are reminded.
And then there's the other side of the spectrum - the meeting-nazis. The meeting organizers who stomp around in anger yelling at people to join their meeting. Or worse - being passive aggressive. There is no cure and no recourse. Just decline if you can, and try not to laugh at their inability to keep their composure. Oh, and good luck!
