By succeeding.

That sounds either snarky or obvious, however, I mean it quite literally. The absolute single best way to create investor fear of missing out, is to actually succeed at what you're doing. There's nothing close to that. Succeed at whatever stage you're at and be able to demonstrate that to the potential investors. If you're the real deal, you can build, execute and deliver on what you're attempting and claiming. Nothing prompts FOMO from investors like actually delivering and building up a demonstrated chain of success as you go; they see it, and they want to be part of it.

All the other methods are shady, deceitful, disingenuous, fake it until you make it types of bullshit cons. Akin to attempting to trick someone into funding you (ha! look at that! I made myself look more successful than I am, I really pulled one over on them; Theranos).