There are, of course, a lot of means to augment your presentation, but the ones most used are the overhead projector and the blackboard. Therefore, we will focus on these two media. Blackboard Using a blackboard in a presentation will present you with runtime as well as compile time difficulties. This will give you problems in your preparation, and might create run time problems. You cannot scribble as you do on paper.
Characters have to be distinguishable from the back rows.
Furthermore, it looks silly when your lines of text turn out to be some sort of sinoid. This might cause murmurs and unwanted loss of attention. Divide the board in blocks. Don't wipe out part of old remarks to put new ones in. Best way to accomplish this is to draw the lines separating the blocks, and only remove whole blocks.