As you've asked for "Best Practices" The Old KISS principal applies here too. Use whatever standard template your company or whomever mandates and then have a

As you've asked for "Best Practices" The Old KISS principal applies here too. Use whatever standard template your company or whomever mandates and then have a Title per slide and Bullet points. If none mandated, just plain white background and standard font size in the default template works best. All transitions etc.... get lost when converting and delay switching time. Only have a single image per slide. The image should be self contained. i.e: Create the diagram in word or other and use image of it. It might look BORING, but it'll be easier to read and the slides are a guide. People should be looking at presenter, NOT at the slides. :)