Prior to drafting a speech outline, I recommend:
- Research the topic. Gather interesting notes, examples, illustrations. In today's world, a "speech" may include visuals like a PowerPoint presentation, a video, posters, etc. -- they are just expected. Know what the audience expects.
- Determine, very precisely, the goals you wish to accomplish. Every speech, every class, every unit, every course must have (1) something to know (for the intellect). (2) something to feel (for the emotions), and (3) something to do (for the will). Imagine a political "town house" gathering where the goal was simply a social get-together with food -- big, big failure ! A great teacher said, "If the student hasn't learned, then the teacher hasn't taught." Both speaker and listener must know the three items mentioned.
- Determine what you need to know about the listeners, the room, the time-frame, the competition/distractions, etc. For example, for a science fair, all listeners are observers, but you must specifically speak to the judges and to their interest.
- Create key success factors, list evaluation criteria, and perform a risk analysis. This means that you know before you start the detailed work that gets an "A" and what gets an "F;" don't even waste you time unless you know that. A risk analysis means to make a list of the most likely things that could go wrong (e.g., power out during your PowerPoint presentation) and what you will already have prepared to do about them. Typically, this is 10% of the effort and it may never be used/seen; but, when you need it, you look like a "star."
- Now, remember that your draft outline is a draft outline is a draft outline -- it is nothing like a speech. It does, however, set the direction and allows easy changes. Work and work on the very terse outline until it is perfect (or as close as you can get). Then, writing a short paragraph for each of the little bullets in your outline will be so easy that many speakers never write any more than just that outline. For a very interesting example, look up Lincoln's notes (or no notes) that he prepared on the train (or not) from Chambersburg for the Gettysburg Address.