Ultimately test various ways to get people to respond and join your list. In the middle of every post It is not overkill to break posts up with a mailing list call to action to join your mailing list. Have some HTML prepared so that you are ready to use it to get people onto your list without causing you to lose your line of thought when writing your blog post. Use the words.
Just before you carry on reading, would you like more information on, pop over here to get" and then carry on with the post. Test and see mailing list how effective this is at building your list by having a different sign up box for each area on your site and keep a document open with the different HTML codes for each area. That way, you can see what is working and what is not working.
Viral marketing will spread as quickly as fire spreads; you will see the results of it all around. Even if the fire cools, the results of what people have read and seen, will stay with them for a long time. They won't forget, and when someone mentions mailing list the relevant niche, they can't help themselves fanning the flames again. The fire never really goes it, it might cool a little, but again it is only a spark needed to ignite it back into actions.