Email marketing doesn't work unless you build a list of people to send messages to who are interested in your products or services. If you've captured email addresses from your prior customers, then you have a great head start. So let's dig into the task of growing your list.

Here are three key steps to growing your email list:

1. Develop relevant opt-in offers

The first step to growing your email service providers list is to develop an offer with a high enough perceived value that your target audience is willing to provide their email addresses in exchange for it. Your offer could be an amazing weekly newsletter, a discount on a future purchase, a free trial or demonstration of your product or a free tangible item, which marketers refer to as an incentive or lead magnet. If your offer isn't valuable enough to your target audience, it doesn't matter how much you promote it online and offline -- no one will be interested enough to take action. That means not only won't you get traffic to your online opt-in form, but you also won't get any subscribers.

With that said, an opt-in form that doesn't promise a special offer or free content as a lead magnet could simply promote all the great content you'll share in your email newsletter. For example, your opt-in form could simply say, "Sign up now so you don't miss the important news and tips you need to be successful."

You can get more specific with your promise with copy that says, "Subscribe now and get a critical tip to grow your business every week delivered directly to your inbox." These examples demonstrate that you don't have to give anything more away than the promise of useful and meaningful information to motivate people to subscribe to your email marketing list.

2. Create effective online opt-in forms

You can create opt-in forms directly in most smtp service providers. It's a very simple process, but there's usually a problem: Most opt-in form designs offered within email marketing tools are very basic. You might be limited by the layout, colors and even the amount or placement of copy. If you're serious about growing your email marketing list, you should consider using a more robust opt-in form tool.

There are a variety of applications you can use to create beautifully designed opt-in forms that can be displayed in a variety of places on your website. Most of these tools offer libraries of free opt-in form templates complete with images, fonts and colors chosen by experienced designers, and many offer free trials or free accounts with basic functionality. Be very careful to make sure the tool and plan you choose integrates directly with your email marketing tool and allows you to capture leads from all your monthly traffic. Some limit the amount of traffic or form submissions allowed at different price points. If your form looks great but isn't displayed to some of your visitors, then don't use it.

3. Drive targeted visitors to your online opt-in forms

Your target audience needs to see your opt-in forms, or you won't be able to grow your email marketing list effectively. Fortunately, there are many steps you can take to bring the audience you want to connect with to your website where they'll see your opt-in forms.

Here are three strategies you can use to drive more qualified traffic to your opt-in forms:

1. Build your email marketing list offline. You can do this by using sign-up forms in your brick-and-mortar location or at conferences and trade shows. It's also important to use offline initiatives to send people to your online opt-in forms where they can subscribe to your list. For example, include the URL for your opt-in form (assuming you have it available on a specific page on your website) on your business cards, print ads, point-of-sale signage, brochures and so on. Lead magnets work particularly well at driving offline leads to your online opt-in forms.

2. Use social media to attract more people to sign up. Social media marketing is an excellent way to drive traffic to your website and your opt-in forms. Post useful information to your social media accounts with links to your opt-in forms. Lead magnets work extremely well to build your list using email marketing blog tactics. You can share sneak peaks from the lead magnet, images, charts, related videos and more to boost interest in your lead magnet and motivate people to click the link and submit your opt-in form. Any social media posts that lead to your opt-in form should be pinned to the top of your newsfeed. You can do this in Facebook, Twitter, Pinterest and other popular social media tools so people are sure to see your opt-in post before they see other posts from you.

3. Advertise online. Online advertising on targeted websites or through Google AdWords, Facebook ads, Twitter ads, LinkedIn ads and other digital advertising services can work extremely well to increase opt-in form submissions, particularly if you're offering a lead magnet that your target audience really wants.

The key to success is to choose laser-focused audiences to show your ads to. Many email marketers working in a wide variety of industries have great success in building their lists by advertising lead magnets through promoted posts on Facebook. The targeting tools are excellent and allow you to hone in on very specific people. Make sure you use a compelling image, in addition to powerful copywriting, and you should see your opt-ins climb.

In addition to traditional digital advertising, test native advertising (also referred to as sponsored posts or paid posts), where you pay a website or blog to publish a post for you with a link back to your opt-in form page. Just make sure the website or blog discloses that the post has been paid for, or you could violate the Federal Code of Regulations' rules related to disclosing material connections in online content.