You have a website. You even have a decent amount of traffic coming in to your website. You have a few sales. But unless your website has this one thing, your website is *shredding* money.

What’s that one thing? The email opt-in form. What’s that? Every sign-up box you see on other websites where they ask for your email address so you can get a discount/get blog updates/get insider newsletter tips/etc. Why are these so important? Two words: email marketing.

The Direct Marketing Association puts email marketing’s ROI for 2011 at $40.56 for every $1 invested.

Sign-up forms are the baseline requirement for email marketing. Hook them up with an email marketing service like MailChimpAweber, or Constant Contact and you have yourself the beginnings of a quality email marketing program.

What makes a good opt-in form? It’s all about conversion – getting your visitors to part with their heavily guarded email address.

Here are a few ideas you can use to increase the conversion rate for your email sign-up on your website:

1 – Eliminate Unnecessary Steps. If possible, have your visitor enter their email address right on the page. Eliminate unnecessary clicks.

2 – Keep It Simple. Do you really need 18 pieces of information about your email subscriber? No. You need an email address, and maybe a name. Don’t discourage sign-ups by requiring your visitor to part with more of their private information and time in filling out your lengthy form.

3 – Make It Prominent, Relevant, and Often. Email opt-ins should be ‘above the fold’ of your webpage – meaning the visitor doesn’t have to scroll to see the form. If they do scroll, add an email opt-in where relevant – the bottom of almost any page on your site is a good example (if they’ve read that much, they’re likely interested in more from you). The only pages on your site where you should definitely avoid an email opt-in are your pages where you want them to press ‘buy now’ or ‘contact me’ instead.

4 – Demonstrate Your Trustworthiness. Visitors don’t give email addresses to businesses they don’t trust. Add a line about your commitment to privacy or not sharing their email address. Logos from Verisign and TRUSTe are good examples. If your subscriber count or Twitter following is high, displaying that number can increase your perceived trusthworthiness. Testimonials also work.

5 – Tell Them What They’re Signing Up For. What sort of information will be in your newsletter? How often will I receive it? What day? Being upfront about this and then delivering as promised will equal a lower unsubscribe rate as a bonus.

6 – Consider Incentives. MarketingExperiments did a study on incentives increasing sign-ups. Incentives can be a great way to increase opt-in conversion rates. Check out my quick video post to for 3 secrets to developing an email marketing incentive that works.

Adding opt-in forms to your website and beginning an email marketing program can equal a huge return for your business. Want more info on email marketing? Check out my recent post – 5 Ways to Get Your Customers to Unsubscribe Today.

Do you have an opt-in form on your site? Did you find this post useful? Let me know in the comments!