There are many ways to give a presentations, but your main objective is to get your message across. Imagine that there is one person in the audience that is only listening and another person that is only looking at your slides (not listening). Both should be able to get your message.
Specifically, the title of your slide should state your main message. For example, rather than a title like “I-V curve of the solar cell,” a better title would be “I-V curve shows 20% improvement with coating.” Also, make sure that axes are clearly labeled, appropriate units are there, and the text is large enough to read.
Below are a few more notes from Jean-luc Doumont that you might find useful: Jean-luc_Doumont_Presentations