One of my top priorities for my travel website is to build a relationship with my audience. After spending hours creating valuable and unique content, you want to share that with as many people as possible. One thing I've found to be irreplaceable when it comes to building that engaged audience: an email list that grew from a pop-up on my website.

Email marketing can help turn one-time visitors into returning readers (and/or customers), ultimately helping you to grow your business. I realize the idea of a pop-up greeting can be perceived as spam. But a well-placed, friendly, welcoming opt-in can work wonders to building a loyal readership.

I have found that a small pop-up that appears on the right hand corner a minute after the user has been on the page works best. Readers were already engaging in content and distracting them from that would be disconnecting them from their experience. I also keep my pop-up user friendly.

Here are four tips to get people to sign-up for your list:

Determine which pop-up flows best with your brand.

When I say "pop-up opt-in," you probably imagine a familiar image: a box pops up in the center of your screen, asking for your email address. It might even take up the entire screen, making that little "x" in the upper right-hand corner hard to find. But there are actually a few different kinds of pop-ups to choose from.

I use the WordPress plugin Sumo Me. It allows me to choose when and where I want my "List Builder" to pop up. It can appear after a certain number of clicks, on a timer, or right before a visitor is about to leave. It also has the options of a banner that stays fixed on the top of a page, a box that scrolls with the user, or the standard middle of the page pop-up.

Timing is everything. I found that anything less than 30 seconds was drawing people away from the content and also irritating readers. If it is displayed too soon, it could get dismissed without a second thought. If displayed too late, the visitor may feel that they've already gotten what they needed.

Use design to grab the right attention.

Virtually all plugins for creating opt-ins will give you design options, although some are more flexible than others. You don't have to know coding or graphic design to make an opt-in that fits your site's look. For instance, the colors I use on mine reflect the colors on my site, except they are more muted. Too much color was perceived as too aggressive but not having color at all made the popup easier to ignore.

Your new opt-in will likely automatically code to show up on mobile devices (but it doesn't hurt to double check). And if you're not feeling super creative you can usually choose from a selection of premade, professional templates.

Test your opt-in and don't be afraid to tweak.

I've found there are a couple of ways to test how effective your opt-in is: A/B testing and analytics. The more you know about how people use your site, the more you can do to boost engagement. With A/B testing, you can choose between designs and text to ensure that you're consistently using the most effective opt-in possible.

Heat Map, for example, shows the most popular links on your site -- by showing a map of where users click most -- helping you to analyze your site's traffic. Sumo Me comes with real-time Google Analytics and Content Analytics that show how much of your pages visitors will generally read. All of that information can influence not only where you put your email pop-up, but how you streamline and design your site to engage more visitors.

Keep it simple.

A pop-up that asks for too much information can be off-putting for many readers and will likely not get many responses. Asking for an email address is usually enough information that people are willing to give but still gives you something to work with.

I grew my mailing list 25 percent faster when I added a pop-up than without it. With any good opt-in service, you'll be able to link up to any of a wide selection of email services who will help analyze your email list's engagement. And with some of those services, you'll be able to target your list to promote your business with new content, product promotions, giveaways, or content upgrades.

Getting the reader's attention and using a call-to-action in a positive way can be a challenge. Thankfully, many email pop-up services are free (though investing in a more sophisticated service is also beneficial). If you design your pop-up with the busy consumer in mind and consider the results of your analytics, you can easily use this tool to keep your audience coming back for more.