Warming up your audience while making a presentation can make it a lot easier by easing the tension in the room.  Also, a relaxed audience tends to react better to the presenter, making your task much easier.  Just be sure to consider the following points when selecting your joke:

1.  Choose an appropriate joke.  You do not want to select a joke that would offend an audience.  Don’t forget that your sense of humor may be different than your audience.  Try out your joke on your friends and colleagues to be sure that the joke will be ok.

2.  Check if poor language skills will hinder the understanding of the joke.  It is very embarassing if you are the only one laughing at your joke.

3.  Some jokes to avoid are sexual, religious and political jokes.  Some people are very sensitive in these areas and you do not want to offend your audience.

4.  Be aware of the cultural relativity of humor.  It is one thing for the locals to make jokes about many things and everyone rolls in laughter, but the moment someone from overseas cracks the same joke it may be viewed as cultural affront.  In the cases you are going overseas, try and pick a neutral topic for your humor - you want your audience eager to hear what you have to say.