Coming up with a funny best man speech is probably the most important job you get when the groom gives you this honour. It is expected that the best man should give a rousing and funny speech and you have a little bit more leeway than the other speakers with what you can say.
If you are not used to public speaking or get nervous when talking amongst crowds then this can be very daunting. Not only do you have to speak amongst an audience but you are expected to be engaging, witty and confident in your delivery.
Many people given the role of best man crack with the pressure and there have been some disastrous speeches at weddings I have been at. Everyone feels for the person but it is little consolation as you only get one shot at it.
To make sure this does not happen to you it is vital to prepare a great speech that will blow people away. Spend a good deal of time thinking of all the best moments from the grooms life and start writing them down. You can edit them into a speech later, but for now just get some ideas down.
If you get the chance try to practice speaking to a crowd and aim to be engaging. You can do this by taking a conversational style and keeping eye contact with various people amongst the crowd. You can have your speech to hand but if you can memorize it then this will be better.
One final tip is to mix in personal stories about the bride and groom with proven jokes that are guaranteed to work. You do not have to be completely original and if you can throw in some crowd pleasing jokes then the audience will show their appreciation.