In my experience, in-person meetings are by far the most effective way of getting your first customers. Video calls with screen sharing (for demos) are the next best thing.

As said by simonw, in-person meeting. That sure would involve email, cold calling and even your website (but as a business card, as I said before).

Define which Small Business is your target, select a few, try to get a meeting with the owners. That shouldn't be hard, after all SMB owners are used to sales meetings (they are not used to decide an important buy only through internet).

After a few (10..20..40?) you will know a lot more about your business.