The most dangerous slide in the world is the one with six paragraphs of text, three nested bullet points, and a graph that needs a magnifying glass. Not because it’s badly designed (which it is), but because it puts the speaker in direct competition with their own visual material. And the speaker always loses.

When you project text, your audience reads. They don’t listen—they read. The human brain cannot process verbal and written information simultaneously. So you have two options: either they read your slides, or they listen to you. Not both at once.

The slides problem

Slides were born as visual support. At some point they became a crutch, a teleprompter, and a compressed printed document on a screen. The result is what we see in 90% of corporate presentations: walls of text the speaker reads aloud while the audience checks their phones.

Why this happens:

  • Insecurity. “If I put everything on the slide, I won’t forget anything.” Slides become the speaker’s script.
  • Tradition. “We’ve always done slides like this here.” Nobody questions the format because everyone reproduces it.
  • Purpose confusion. The presentation is used as a document to email afterwards. That’s not a presentation—it’s a report in landscape format.
  • Lack of visual judgement. Without design training, people fill empty space because emptiness makes them uncomfortable.

The fundamental rule: slides are for the audience, not for the speaker. If you need notes, use presenter view or physical cards. Slides should contain only what helps the audience process your message.

Visual design principles

You don’t need to be a graphic designer. You need to follow five principles:

1. One idea per slide. If your slide conveys more than one concept, split it into two. Each slide is a unit of thought, not a section summary.

2. The 3-second test. Your audience should understand the slide’s message in three seconds or less. If they need to read for thirty seconds, you’ve put too much.

3. More visual, less textual. A powerful image communicates more than three paragraphs. A single large statistic on screen impacts more than one buried among bullet points.

4. White space. Emptiness isn’t error—it’s visual breathing room. Content surrounded by space gains prominence. Don’t fill every centimetre.

5. Typographic consistency. A maximum of two fonts. Minimum 24-point size so it reads from the back. If text can’t be read from the last row, it’s unnecessary.

Effective slide types

The single-data slide. One large number, one context sentence. “73% of employees don’t trust their leaders.” Impact comes from isolating the data point.

The image slide. A full-screen photograph that evokes the emotion you want to generate. You provide the words; the image provides the feeling.

The diagram slide. A simple diagram showing relationships between concepts: arrows, circles, flows. Maximum 5-7 visible elements.

The quote slide. A short, attributed sentence that reinforces your argument. No more than 12 words.

The contrast slide. Two columns: before/after, problem/solution, myth/reality. Visual and immediate.

The blank slide. Yes, a black screen or one with just your logo. When you want all attention on you, turning off the screen is a legitimate and powerful resource.

Errors that kill presentations

Error 1: Reading slides. If your audience can read (and they probably can), they’re reading faster than you. When you reach the second point, they’re already on the fourth. There’s desynchronisation and boredom.

Error 2: Death by bullets. Endless lists of points with sub-points. There’s no visual hierarchy, no focus, no impact. Everything seems equally important, so nothing is.

Error 3: Illegible charts. Excel tables copied directly. Graphs with 15 series and microscopic legends. If you need to say “I know this doesn’t show well, but…” don’t include it.

Error 4: Excessive animations and transitions. Text that flies, spins, and bounces distracts from content. Animations should be invisible: appear and disappear, nothing more.

Error 5: Saturated corporate templates. Logos in every corner, colour bars, footers with date and slide number, decorative frames. All of that steals space from actual content.

Error 6: Too many slides. One slide per minute is a healthy rhythm. 80 slides for 20 minutes is a carousel that causes vertigo.

When not to use slides

The question nobody asks: do I need slides for this presentation?

You probably don’t need slides if:

  • You’re in a meeting of fewer than 10 people where debate takes priority.
  • Your presentation is pure narrative (a personal story, a reflection).
  • You’ll speak for fewer than 5 minutes.
  • The space has no projector and forcing a small laptop doesn’t add value.
  • Your topic is so emotional that slides would subtract intimacy.

You probably do need slides if:

  • You have quantitative data that needs visualisation.
  • Content includes flows or processes that are hard to follow verbally alone.
  • The audience is large and needs visual anchors to maintain attention.
  • Your material will be shared afterwards and needs visual support for recall.

The middle ground: minimal slides. 5-8 slides for 20 minutes, each with an image or data point that anchors a section. They don’t tell your story—they punctuate it.

The best slides are the ones the audience doesn’t consciously remember—but that made the message clearer, more visual, and more memorable without them noticing. They’re support, not protagonist. If your slides can give the presentation without you, they’re too much. If you can give the presentation without your slides, they’re well calibrated.

In the next chapter we move from preparation to practice: how to rehearse intelligently to build confidence without losing the freshness that makes you human in front of your audience.