Keep your slide background simple - don't present text over watermarks or images.
Use simple fonts and try to keep the font size above 22pt.
PPT Layout Templates
Use the layout templates provided in PowerPoint.
Use the Selection Pane option under the Format ribbon (or the Arrange menu from the
Home ribbon). The order in which items are read will be listed from bottom to top
- the first item read will be at the bottom. You can use this tool to reorder the
read order, if needed. Remember, the title should always be read first.
The title of each slide should be unique. This allows someone to know what info is
on each slide. If the title is the same between slides, then it is unclear how/why
the content of the slides has been broken into multiple slides. If the info does span
multiple slides, include "continued" in the title to indicate that the info is spilling
over from the previous slide.
Just don't do it. Often shapes are used behind text to create emphasis. Most screen
readers will not identify shapes, and you will often split up your text in awkward
ways to make it fit withing the shape.
Any transitions you add to your slides should be done using the "on click" option,
versus timing the animations and transitions. This allows the user/viewer to control
the speed at which they view the content and progress through the slides. You can
adjust this setting from both the Transitions and Animations ribbons. If you must
use transitions, keep them simple and untimed.