In every possible place ask your reader to sign-up for your newsletter.
Offer them something valuable (called an opt-in that is a digital pdf download, email course, etc.) to help them solve a probelm in your niche (why they are visiting your blog) as a thank-you for trusting you with their email.
STEP 1 ‣ Decide what your opt-in is going to be (eBook, guide, checklist, cheat sheet, swipe file, email course, etc.)
STEP 2 ‣ Create your opt-in. I use Microsoft PowerPoint to create most of my opt-in documents.
STEP 3 ‣ Create the actual opt-in form(s) for the download (where the reader clicks and then is taken to the newsletter sign-up.)
STEP 4 ‣ Connect the digital download to the opt-in form so it is on the thank you page as soon as they sign up, or put it in the welcome email they get as soon as they sign up (this is the option I use.)