To save yourself and everyone else, another best man speech rule to remember is to keep it short. Don't make it a 1 minute speech that sounds like you just met the guy but it does not need to be a 15 minute speech about all the good times you used to have either. A best man speech rule that is sometimes overlooked is to be funny, it is a wedding and there is a time for seriousness but this is a time when you can tell a funny story or use a great line he has said, plus with humor, it tends to take some of the pressure off as soon as you see someone chuckle at a joke or quote.