Use overheads containing mostly short bulleted lists, diagrams, and charts . A picture is worth a lot more than a thousand words. Use large type . Anything smaller than about 24-point will be hard to see in a large room. Charts are better than tables.
Lower case is better than all capitals .
If anyone wants details of the math, they can ask for them later. If you show flow charts or plots, make sure they're completely labeled . A chart with lots of unlabeled blocks and lines with arrows is pretty useless, as is a plot of W vs. x with no clue about what W and x are. Plan a closing line . Rehearse several times and make sure the timing is right .