1. Have a single and singular goal for your talk.
Obama saw the speech as an effort to "speak the truth" about U.S. relations with the Muslim world.
2. Determining tone is as important as choosing the content.
Together they create the metamessage that the audience will grok. Considering your audience, what is the main tone you want to embody with your audience? Obama, for example, giving his first speech from a "major Islamic forum" chose a respectful tone to maximize the chance to be credible with his bold – some say blunt - content.
The secondary and reinforcing tones were steadiness and strength. They were vital when Obama took (content) stands that alternatively discomforted different audiences he wished to reach.
For example, bringing up women’s rights upset some Arab audiences. And “Some Israelis and American Jews recoiled at the way Obama juxtaposed the suffering of the Holocaust and centuries of anti-Semitic persecution with the experience of Palestinians under Israeli occupation.”
3. Ask for insights from people who have first-hand knowledge of the audience. You may not have a speech-writing team like Obama yet you can get some first-hand insights rather easily.
That’s why, as a public speaker I ask the meeting planner who hires me for the names of three disparate leaders in the group. I interview them in advance, beginning with open-ended questions. A helpful starter question is “What are the top-of-mind issues for opportunities for them?”