We've built a great product. Now what?

Previously, I had a post about Google Plus, the great party everyone showed up to, and a minute later went home.
After talking to some entrepreneurs recently, It seems like getting the crowd to take a look at your product is one challenge, and then getting them engaged over a period of time is even more challenging.
So after identifying what the world needs, and how to give the world exactly what it needs, got some feedback from friends, all that's left is bringing people in.
A few tips on doing that without spending on ads and promotion:

(I'll use a flower shop analogy).

- Try to think of one great benefit your potential user (Customer) receives from your product. Formulate that into a strong message. ("We promote flower shops" -> "The best way to promote your flower shop").
- Look for where your potential user hangs out (Online flower shop owners online forum). Stalk it, see how you can begin promoting yourself there.
- Even better - Find out your 'dealer' there (A power user...). Do what you can to lure him: Promise him to be featured for free. Make him get the customers to you.
- Now find 10 of these...

Marketing used to be based on ads, impressions, clicks.
Reliable, engaging marketing is based on opinion makers.

Or, you can do like these guys.