It’s important to collect email addresses to build your email marketing list.  Here is a list of where you should include the actual sign up form or a link to one on a web page. If you can include the form yourself, great! If not, atleast link to it.
Your Homepage – If you don’t have one on your home page, get one there now.

Your Sub-pages – All of them! If you don’t have the space to put an actual form on all of your sub-pages, at least have a “Newsletter Sign Up” link on them.

Your Blog - Not everyone subscribes to RSS to get information from your blog, so you’ll need to include an actual form for your readers to sign up, or a “Sign Up For Our Newsletter” link to it. You don’t want to lose the opportunity to get email addresses from people who might be interested in knowing about your regular updates.

Your Purchase Confirmation Page – Someone has just hopefully had a great experience purchasing from you, why not ask them to join your list right then and there?

A Landing Page – If you have a separate landing page you send people to from your search engine pay-per-click campaigns, include a newsletter sign up form on it. If they don’t purchase from you, they might at least sign up to your list, then you’ll be able to attempt to get them to purchase later on.

The Footer of all Outbound Emails – Any email you personally send or any email your employees or customer service people send one on one, should have the link to your opt-in form.

This is just cover the basics. There are a lot of other creative ways to opt -in people. Look for more listings to come about this topic.