1. I think it's really ineffective to cover a slide with words and then proceed to read them to the audience. It's overwhelming and definitely not visually appealing or interesting to sit through.
2. It also really bothers me when people use a different slide transition for every slide and then a different animation for every element on the slide. It's kind of like when people use tons of different fonts on a Word document. It may seem like it adds interest but it just looks really unprofessional and actually makes it much more confusing.
3. Using the preset slide layouts that Microsoft provides isn't a good idea because people have seen them all before and it just ends up being another way to make things look unprofessional and unoriginal.
4. It may seem like it's more exciting to make every slide look completely different, but I think in most cases that just, again, looks unprofessional. If the slides are consistent, people pay attention to the information instead of being overwhelmed by slide design changes.
5. Probably the most important thing is to remember to keep it simple because the powerpoint should just visually enhance your presentation, not give the presentation.