Acting as a master of ceremonies (emcee) is a challenge for anyone. The emcee is responsible for moving from one segment of an event to the next and smoothing the transitions between so the attendees are never simply sitting and waiting for someone to do something. Many emcees use jokes to keep an audience engaged.
Give careful consideration to the type of jokes you tell. Racist jokes, jokes about sex, jokes that make fun of someone's religion and jokes about people's appearances are likely to offend someone in the audience. This will not only reflect badly on you but on the people you are introducing and those organizing and sponsoring the event.
Avoid jokes that have been told and retold many times in favor of funny anecdotes about people in attendance. Be careful, however, to avoid humiliating anyone. If you're not sure whether you should tell the story, actually ask the person who is the subject of the story if it would offend or humiliate him.
Be selective. You only need to tell a few jokes and only when there is a long break between events that need to be filled with your voice. Remember that the attendees are not there to hear you, but are rather there to see and hear the people you are introducing.
Have a joke ready for situations that may come up during the evening. For instance, if a waiter drops a tray, you can smooth over the awkward moment with a joke.
Keep the demographics of your audience in mind when deciding whether or not to tell jokes about current events or celebrities. For example, an older crowd probably won't appreciate or maybe even understand a joke about young Hollywood, while a crowd of people in their 20s or 30s would probably really enjoy that. If the crowd is mixed in age, keep your jokes of a general nature.
Toastmasters International can help you learn how to be an effective emcee. Check in your local area for a club to join or start one yourself. Remember that although your performance as emcee is an important part of events, you are not the person the audience has come to see.
There's nothing worse than an emcee that isn't funny but doesn't know it. Try your jokes out on a few people and get their feedback. You may have to practice a joke before it works, or you may have to admit to yourself that you're just not funny enough to tell jokes. Don't tell "inside" jokes that only you and a couple of other people understand. The rest of the audience will feel left out. Consider letting the audience in on a formerly inside joke instead.