Your presentation should have:
Your introduction should include an outline of the areas you are going to cover in the presentation - your audience needs to know what is coming. If your purpose is to give your opinion make sure your audience knows what you think right at the beginning. Signpost the structure of your presentation by stating clearly when you are moving onto the next section.
Your middle section should explore your three or four main points in detail.
Your conclusion should give your audience something to remember. Tell them again why this is an important topic. If you can, ask them to do something. For example, if your presentation has been about damage to the environment, you could end by giving the audience practical suggestions about what steps they could take which would make a difference.
Slides and other visual aids can enhance your presentation, but they should be used carefully. Avoid writing out your full idea on your slides - it’s far better to have a well-chosen image with few words. It will also be more memorable than extended pieces of writing. Your audience are there to listen to you so don’t give them lots to read as well. In general, the fewer slides you use the better. Use them to introduce each of the main sections of your presentation.
Video clips can also be effective, but make sure you explain why they are there. Generally, clips should be short, linked to one of your points and add to your arguments rather than just repeating what you have said.
Make sure you speak loudly enough for your audience to hear. When people are nervous they tend to talk quickly which can make them difficult to understand - make a conscious effort to slow down and breathe. Try to avoid fillers like 'umm' and 'err' which can be distracting. You should also vary your tone of voice and sound as if you are enthusiastic about your topic. If you don’t seem interested then it’s unlikely you will be able to interest anyone else.
You are not just presenting your topic, you are presenting yourself. Rehearsing in front of a mirror or filming yourself can help you identify any issues with body language. Stand up straight and avoid fidgeting as this can be distracting and give the impression you are unsure of yourself. Show you are confident by looking at your audience and use gesture to emphasise points. Try to smile - if you look like you are enjoying yourself then your audience is much more likely to enjoy the experience with you.