Ensure the audience can hear the joke so not a word is missed. If your talk starts with a joke, make sure it is brief. Any humour should be directly related to the subject. Public humour leaves no room for sarcasm or contempt. Vocabulary Express your meaning with clarity to produce vivid, memorable phrases.
Words are tools.
Also make a note of any unusual words you intend to use and check their exact meanings. Jargon Technical, complicated or unusual words should not be used just for their own sake. The best language is simple language. Short, direct words in short, clear sentences are the basis for forceful public speaking. Diction Diction is the way you say words.