Talk to every small business in your city or neighborhood. Give them an X-day free trial and a sign/sticker that tells customers what to do.

Give customers an incentive to give suggestions if they're not doing it on their own. Pay out of your pocket (IIRC Yelp did something like this, paying for reviews) or helping vendors subsidize things at their store, e.g., give a review get 5% off your next purchase.

That's what I'd do, anyhow.