Something we teach all year 7 - 'audience and purpose'. This should underpin your entire presentation; from font choice and size/colour, slide colour design/layout, use of images etc.
Don't put too many points on one slide - it needs to be easy to read from the back of a room.
Avoid custom animations/transitions (although some smooth slide transitions do no harm). Also be careful with how you advance your slide - use the slide timer to see how long it takes to move through each point, to move most automatically. However, you should manually move the slide itself. It looks very professional if you can leave the points to come on automatically but still keep control of the slide themselves.
Practice and practice your slides, add some points of interests (graphs etc - make them clear!) if you can. It should support your presentation, not overbear it.