Planning a presentation
Good presentations don't happen by accident, they take time and effort.
Doing work ahead of time will ensure that you both feel and sound more confident and authoritative. If you understand your topic better you will deliver a better talk. Preparation will help make sure you deliver the right message and don't say something wrong.
Ashish Arora's article Presentation Success Formula: How to Start Strong and End Powerfully provides useful advice.
Think about how to start.
First impressions are important and happen very quickly. Your audience will make a snap decision about you within the first few moments. At the very beginning of your presentation gab their attention and ensure come across as interesting and authoritative.Think about how you want to come across.
Don't just fade away. People remember the end (see e.g. Daniel Kahneman's work). At least let them know that you have consciously finished at that point, not been cut off. Try to wrap things up neatly and with enthusiasm.
Think about the phases of a talk.
Start with the BIG issue. Then go into the details. Finish with the KEY takeaway.
There are no hard and fast rules.
A minute on google will provide you with a lot of rules for a good presentation. Remember what works for one person in one situation might not work for another person or in another situation. It will depend on your audience, and on how you deliver it. Find what works for you.