=> Make points that folks agree on first. Never create controversy early, unless you are doing it for dramatic effect.
=> Never tell a long involved story unless it is HIGHLY TESTED. If it bombs, you will have a tough fight to win back the audience.
=> Never tell any story or joke that has a remote chance of offending someone. After you warm up the audience, you may be bolder.
=> Somewhere in your opening you must tell the audience why you are there. They need some selfish reason to listen to you.
=> Using humor in your opening tells the audience that yours is going to be a fun presentation. It tells them that they might actually enjoy it. Don't disappoint them by telling an opening joke and boring them the rest of the time.