There are only five ways to make something look important

Emphasis is comparative, and there is a short list of comparisons

Nothing on a page is important. Things are only more important than the things next to them, and there are five ways to arrange that. Every hierarchy you have ever admired is some combination of these.

1. Size. The biggest thing is read first. Crude, reliable, and the one most people reach for.
2. Weight and density. Bold against regular; a solid block against an outline; a dense cluster against a sparse one.
3. Contrast against the ground. Dark on light, light on dark, one saturated colour among muted ones. This is the strongest lever at a distance and the one people under-use.
4. Position. Top and left in left-to-right reading cultures; the optical centre, which sits slightly above the geometric centre; the end of a sequence. Where something sits is a claim about when it should be read.
5. Isolation. A thing alone in space outranks a thing in a crowd, regardless of its size. This is the lever that costs nothing but nerve.

The rule that does most of the work: use two

One lever is usually not enough to be seen. Three or more is shouting, and shouting has a mechanism behind its failure. Each lever consumes some of the design’s available contrast: the total difference the viewer can perceive between elements. Spend it all on the headline and the second-level items have nothing left to distinguish them from the third, so the hierarchy collapses from three levels into two: the shouting thing, and everything else.

So: big and isolated. Or bold and high-contrast. Not big and bold and red and centred and boxed, which is what a flyer looks like when five people each added their own emphasis.

Make the gaps obvious

A hierarchy fails more often from insufficient difference than from the wrong choice. If your headline is 28pt and your subhead is 24pt, the viewer does not perceive two levels; they perceive one level with an inconsistency in it. The difference has to be unmistakable at a glance.

A practical starting scale, which you should then break on purpose:

level 1   48pt bold
level 2   24pt bold      (half)
level 3   16pt regular   (two thirds)
support   12pt regular

The ratios matter more than the numbers. Roughly 1.5× to 2× between adjacent levels reads as deliberate; 1.1× reads as a mistake. Type scales built on a fixed ratio, 1.25, 1.333, 1.5, exist for exactly this reason, and every one of Inkscape, Scribus, Figma, GIMP and Photoshop will let you type the resulting numbers straight in.

Isolation is the cheap lever nobody pulls

If you cannot make the important thing bigger, because the format is small, make everything else smaller and move it away. A 16pt line alone in the top third of a poster outranks a 40pt line wedged between a logo and a QR code. The eye finds edges and isolated figures fast, before it has resolved any detail, so an isolated element is registered as a distinct object while a crowded one is still part of a texture.

This is also the lever clients resist, because empty space looks like unused space and unused space looks like something you did not do. The counter-argument to have ready: the empty area is not empty, it is the reason the important line is readable from across the room.

What the levers cannot do

They establish rank. They cannot establish meaning. A perfectly ranked design in which the largest element is the wrong message is a well-built failure, and this is much commoner than a badly ranked one. Before you apply any of this, the sentence from the brief has to be settled, because hierarchy is an amplifier and it amplifies whatever you put at level one.

They also have a cultural boundary worth knowing. Position as a lever assumes a reading direction. In a left-to-right script, top-left is the strong entry; in an Urdu or Arabic layout the strong entry is top-right, and mirroring a layout without rethinking it produces something that reads backwards to the people it is for. Size, weight, contrast and isolation carry across scripts; position does not carry for free.

The check

Name your three levels out loud before you open the file: what is read first, second, third. Then, after you have built it, hand it to somebody for two seconds and ask what they saw. If they name your level-two element, you have spent your contrast in the wrong place. And the fix is almost never to make level one bigger. It is to make levels two and three quieter.