It depends on what kind of business you are targeting-- what's the niche?

If you have a clear idea of who your target customers are, you can intuit what methods would be most appropriate to use to promote your service to them. For some niches, this could be cold calling. For others, there might be trade shows or publications.

In my previous startup, we had a tiny, very focused niche (where about 25 firms were responsible for more than 75% of the revenue in the industry), so we did no marketing at all, and instead focused on cultivating personal relationships with the decision-makers of the top 10 firms. But that approach would be wildly inappropriate in other situations.

So: it all depends.