I just wanted to add a few more points that will add detail to your advice:

1. You can add subscription box to blog, too, not just websites. The wordpress plugin that allows you to do this escapes my mind at the moment, but I know it’s possible.

2. About high-value content: Reflect what’s going on today. Current news and how it relates to your target reader usually equals high value.

3. In your link to your site, let your anchor text be the keyword phrase you want to rank for. The anchor text is the clickable text, usually written in blue lettering.

I have a number of writers, too. You have to work hard to build your list with the people who will hire you. Make sure your Website (or blog) is optimized so that people looking for your writing services will find it. (That is why I advise putting a subscription form on each page of your site.) Offer a report your target audience will find useful, not other writers. Ditto for your newsletter content.

Each time you meet a prospective client, ask if you can add him or her to list. Each time someone inquires about your services, ask if you can add them to your list.