[muzani]

"existing market solution or manual efforts"

This is really the core. How bad are the current solution? How painful is the manual effort?

If the status quo sucks, then you don't need to do any convincing, they'll run to you, beg you for the wishlist. Your job is to make sure it's visible to them. Make sure it doesn't smell like the other startups with crazy claims (i.e. don't say you're top on Product Hunt). You can put ads. You can walk up to them and tell them. You can talk about it on radio. You can post posts on reddit.

Many of these approaches only work for the initial product market fit stage though. Then you have to start thinking about distribution. But distribution is an easier problem.

You'll also fail a lot - most of the time the first thing you make is terrible. But you have to put it in front of someone to figure out what they really want. Assume that first iteration is a the block of marble and not the statue you're trying to carve out of it. The carving only starts after someone rejects it. You carve out a little bit of what the statue isn't, until you end up with the masterpiece.