Thinking about writing some comedy dialogue, well start planning. Who is your Audience, write about things that happen to the group your writing for, they will enjoy it more. What does your audience do, mention at least one important person in that audience, this gives a personal touch.
Whats the theme that your writing, build it around your audience and the event or holiday. When writing put the best part last, the second best part first, and place quick, fast paced lines in the middle. Your character should have short punchy responces for quick laughs., and should get most if not all of the funny lines. Be sure the audience hears and understands everything the Figure says, got something of importance for the audience to hear let the dummy say it. Disagreement should be first thing on your mind when writing the dummys part. The bigger the problem, the more the audience will become involved. The solution to the conflict should come to a surprise finish, when I say suprise I mean a twist, something that is fun to hear. Know your figures character, that basically means know your character as well as you know yourself, to make the figure believable. You want the audience to be on the dummy's side, this is a very important aspect of the dialogue. Be a good actor, remember your playing 2 roles and making them both believable. You need not write blue comedy, keep your lines nice and clean. When writing you are the only one that needs to be humiliated, no one else. Think of good, creative, clean jokes that will follow the theme and fit your character's personality. You can change old jokes to fit the situation. This is very important, be original, don't steal someone else's thunder, but you can recreate the lines and make them your own... but always try to create your own ideas. The audience loves to hear your figure sing so open with a song and or close with one. They don't expect the figure to have a beautiful voice; so if you can't sing well, it doesn't matter. Make the song follow the theme of the dialogue. You can even change the words of a familiar song to make a funny parody. It is extremely important to stay within the performance time given to you. Keep your routine fast paced. Don't let it drag! Try to end your act with your audience wanting more. And then be prepared to give it to them.