Size, layout, font (typeface) and size, colors

Size - A4

Layout should be pleasant and easy to read: horizontal/landscape layout is preferable.

If possible, use color transparencies (unless you are just showing text).

How many?

One every two minutes is sufficient. To show too many slides is worse than none at all.

How should you present a visual in a presentation?

It is not sufficient just to put up a transparency on the screen and expect the audience to turn its attention to it, to understand it and make the link with what you are saying. The following strategy can be suggested:

1) It is important to prepare your audience for what they are going to see. This keeps the audience on their toes and gives you the opportunity to position your visual correctly.

Let's look at the current distribution of the market, as you can see...

I'm going to show you now the most recent figures available...

My next slide concerns the method by which...

2) Remember to draw the attention of the audience to the points that you wish to highlight but avoid redundancy by describing everything that is in the visual!

As you can see....

The first line of figures is the most revealing...

Notice/observe how the increase has had an effect on the...

What is important here is the way that...

3) You can also try to rephrase your point to give it emphasis, giving the audience time to absorb the information.

In other words the number of employees has a direct effect on the...

Or to look at it in another way every time you...

That is to say no matter what technique is used, the results remain