What are your best email marketing techniques?

I'm building an email list for my weekly accountability call with other solo founders @ CommitCalls.com.

I have just over 20 subscribers so far, and I am wondering how to take advantage of this small but growing list. So far the call's attendance has been less than ideal.

Also, if anyone has any successful techniques or patterns that they use, regardless of context, please do share. Just reading Courtland's message about the flow of "sending a reminder to product page owners to post their milestone" is super curious.

Thanks,
Aidan