In powerpoint ,you should write only clues from your topic but not full sentences. You should not decorate and make your powerpoint presentation look very interesting because all audience will pay attention to your presentation not you. But you should be the main thing in there. background color should be a color that your text is clearly seen on it. Your presentaion should not have any sounds or something that makes us see the screen instead of the main person that presents. It should be simple and a little interesting. If your presentation has the same backgrounds for all slides, it is more better. The more simple with good information and an eye contact all the time and explaining clearly, the more better your presentation looks like and everybody will like it and also you will get full mark.