An experience they can't live without.
We do this at @usefyi by creating a fake @ProductHunt page *before* we launch. Inspired by @Amazon's working backwards process.
Here is @Werner’s explanation of Working Backwards from 2006 allthingsdistributed.com/2006/11/workin…

Who are our customers?
What do they need?
bits.blogs.nytimes.com/2009/12/24/is-…

He says that “Iterating on a press release is a lot less expensive than iterating on the product itself (and quicker!)”
quora.com/What-is-Amazon…
It has the most detailed explanation of the process that I have found.
He walks through the launch of @amazonmusic unlimited as an example: medium.com/@kintan/custom…