Something I see neglected in the comments is emails. I assume you had a life before you started this venture and have met people in business and personal situations and emailed back and forth with them.

Your personal email list is one of the best ways to drive initial traffic and build awareness since:

1. These people know you and (hopefully) trust you 2. They're likely more willing to provide additional connections and introductions

When you have a rough estimate of when you want to launch your startup you should be emailing the relevant contacts on your list regularly to keep them up to date on what you're doing and when it will likely be ready. That way when you launch and are trying to drive traffic you already have an initial audience who can forward it on to their contacts.

Past that... yes you should definitely emailing relevant writers with your story, blogging, and generally creating as much great content as possible and seeding it online in the places that matter to your startup.