If you have any control over the topic (Sometimes you do, and sometimes you don't!), choose a topic with which you are comfortable and can discuss well. It is much easier to present on a topic with which you have a meaningful connection, and this will make it easier for you to convey needed information to your audience as well.
Thus, also consider the needs and knowledge level of your audience. How much do they already know about the topic? What will the setting of the presentation be like? Is it a large group, which prevents much interaction with the audience, or is it a more intimate setting, which might allow for questions and answers? You want to present the information at just the right level of difficulty/expertise. If, for example, the topic is much more complex than the audience's overall knowledge, you will need to find ways to break the topic down into meaningful subtopics to help bridge the gap between what the audience knows when you begin your presentation and what you want them to know when they leave. It is important to sound knowledgeable, but it is also important to make the information meaningful and relevant to your audience.
When you begin planning the presentation, start with the end in mind. What is the key objective that you have for your audience? What do you really want them to leave with a better understanding of? When you are clear on the end goal, it is easier to then create a plan that allows the presentation to reach that goal.
Start with an interesting introduction. Is there an incredible statistic relating to your topic? Do you have a funny story that will engage the audience? Can you find (or take) some photos to include that will bring the presentation to life right from the beginning? If you can "hook" your audience at the beginning, they are more likely to stay with you.
Organize the information in a coherent way. If you are utilizing a visual aid such as PowerPoint or Google Slides, be sure to limit the amount of text you include on each slide—and don't underestimate the impact of well-placed images. It really helps if the audience can visualize the concepts while you are presenting. If you use video or audio clips, choose very short clips that don't detract from you—the core presenter.
End meaningfully. Consider that goal which you had for your audience when you started. Are you sure you have reached that goal? Can you think of a way to make this goal more personally meaningful to your audience? What impact could this information have on their daily lives? How could it shape their thinking or actions?
Practice the presentation. If you have created materials, be sure to have someone edit and look for grammatical mistakes. Practice making eye contact and be sure you are not simply reading from notes. Be comfortable and confident enough with the material that it is nearly memorized. You should use notes only as reminders. Look for key words and then be able to speak fluently about the topic from those notes. Practice maintaining good posture and voice control. (I always tell students to speak slightly louder than typical conversation volume to both offer a sense of commanding presence and to be heard by those who are farthest away from the speaker.)
Be sure to dress well. You want to appear well-prepared, and dressing the part goes a long way. You don't have to look like you're headed to the opera, but you should look well put together and that you have intentionally dressed knowing that you are delivering a formal presentation.
I hope this helps with your planning. Good luck!