Some good advice from Vinicius Vacanti about how to go about getting those initial users. Vinicius focuses on online methods, and so advises first getting a domain and landing page to capture interest in the form of email addresses, and then driving traffic to it by the following methods:
- Email signatures
- Web profiles
- Demo videos
- Networking events
- TechCrunch and tech blogs
- Hacker News
- Facebook Ads/Adwords
- A company blog
All good methods (except perhaps for paying for advertisement, unless you're trying to do some kind of MVP hypothesis testing which you feel is worth the expense.
It's worth remembering, also, that customer development doesn't have to happen online. In fact, the primary customer development method for a b2b business is likely to be offline, face to face with potential customers.