What marketing strategy has a 4,300% ROI? What’s the #1 preferred channel by customers for marketing messages? What marketing most effectively turns clients who’ve forgotten about you into return and repeat clients?

It’s not Twitter or Pinterest. It’s not mobile advertising. It’s the 20-year-old "dinosaur" of the internet: email.

Every freelancer should have some kind of email marketing campaign, because:

• Email marketing takes less time than you think it does
• It costs less than any marketing you will do
• It’s more effective per $1 spent than any marketing you will do
• You should really just do it.

What do you want to accomplish?

1. I want to increase my online brand presence and take over the world.

Email marketing will be part of your strategy, but if you want to become the next medium-sized online brand thing, come back to this post later and start by reading these great books:

Likeable by Dave Kerpen, Content Rules by Ann Handley, The Small Army Strategy by Srinivas Rao.

2. I want to share content I already have (it just needs the right packaging) or create new content, so that current contacts might share it with their contacts and I get new clients.

Great! This post is for you. Keep reading.

3. I want to send personal messages to my past and current clients.

The only strategy you need to know is: a) when you email them, remind them who you are, b) use holidays, birthdays, industry news, their news (which you got by following them on social media) as an excuse to email them, c) check in on them and thank them, don’t (always) ask for stuff, and d) don’t wait until you need a job to email them, do it regularly. The rest of this post probably won’t interest you much!

The obvious secret to every kind of digital marketing

“Be helpful on subjects where you’re knowledgeable, and you build visibility, trust, and a following.” That’s from Freelancers Union’s founder, Sara Horowitz. Let’s break it down.

Be helpful. The best email campaigns are filled with interesting, informative, or inspirational content that you are giving away for free. Every email you send should be 90% good for your client, 10% good for you. By giving away little nuggets of your expertise, you are demonstrating your value as a freelancer to prospective clients. (By the way, never be afraid that by giving away your information you’ll be out of a job.)

On subjects where you’re knowledgable. So if you’re a copywriter, you can give away everything from proofreading tips to how to write the best headline to how to work with freelancers to productivity tips. Remember, don’t only share your knowledge, convey what your reader can do with this knowledge and how it will help them.

You build visibility. People share interesting, informational content with their friends. It’s like they’re passing around your business card for you.

Trust. You’re building others’ perception of you as an expert -- maybe even in areas they didn’t know you were an expert in.

A following. Which by they way happens sloooowly, depends on frequency of email communications, how niche-y your content is, and whether or not you combine email marketing with social media marketing. Also, remember that a small, loyal following is in many ways more powerful than a loose, larger one. So don’t judge your success on size.

No matter what you want to accomplish, don’t be too salesy.

You are building your authority as a likeable expert. Your goal is obviously to increase your business, but think of that as a long-term goal.

BUT. Including a new product or service in your email -- especially if it’s paired with your usual useful or interesting content -- is a good idea. Remember the 90-10 rule above? Make the new service secondary and the stuff that’s useful for them primary.

OK, but tell me what I should say!

Obviously what you share in an email newsletter depends a lot on your field/skill set. But here are some ideas, just to get the wheels turning:

Blog round-up. If you already write for your blog, pick your best blog post and put it into an email. Cut it off early with a “Read More” link back to your blog. Then title your other blog posts or interesting links above or beneath the longer content block. Why have longer content? Because the majority of your readers will not ever click in an email, they will just read. You want to please them (by giving them accessible content) and lead the people who want more back to your site (with the links).

Be a collector. Curate and share other people’s stuff, with your frame/intro/curatorial touch. The internet is a big confusing place, and you can be their guide through your field. For instance, if you’re a social media marketer, start a Best of Social newsletter where you share weekly or monthly highlights of great social media campaigns/ads. Check out Daily Candy, Ideal Bite, or GeekChicDaily for inspiration. Note how careful they are to make sure you know the content is not theirs whatsoever. Never share other people’s full blog posts in an email.

For photographers. Send out one recent fun or inspiring picture you’ve taken -- perhaps seasonal themed -- with a short 1-2 sentence note, wishing them a happy season or giving them a quote about spring or what have you. Contact info in the footer.

Film people. Do the same as above, but with a video you’ve created or a clip of a video.

Support a cause. Share a charitable cause you are supporting. Should be part of a mix of email types, not regular.

Tips in lists. The most popular thing on the internet, lists, really work. Even people who are still sick of lists read lists. Try “Five tips for Improving Your Business with _____ (the skill you have)”. Make ‘em bullets, and make it short.

Share your clients’ success stories. This is an especially good idea for freelancers who work for small businesses. Your clients will love you when you say, “I’m going to advertise this exciting thing to all my contacts!” and when you communicate the story, include “what I learned” bullets at the bottom -- communicating the story into actionable tips for your subscribers.

Discuss and explain. Continue or comment on an issue/discussion currently in your field, and explain it to non-experts in your field. Hopefully nothing that would isolate a large segment of your subscribers. For instance, “What’s all this about 48 fps in The Hobbit?” comment on the discussion and make your own claim.

FAQs. Have questions that clients always ask you? Write a FAQs and share it in your regular email campaign.

Recap an industry event you just attended.

Get ideas from your clients. Remember to chat with your clients and ask them what they don’t know about what you do. Get inspiration for things to talk about/explain for your whole audience in 300-600 words.

Cartoons are fun. Use a cartoon to illustrate something you’re talking about. (You can buy a license on a site like cartoonstock.com.) Easy way to make your content shareable.

Show you’re learning. Distill something that you’re learning into easily digestible bits. You don’t only need to talk about the things you’re an expert at. (Just make sure it’s interesting to your audience.)

There are a thousand other options, obviously. But the point is to sit down with yourself and ask to find the happy intersection between what you’d enjoy talking about and what your clients would actually read.

How often should I send emails?

Depends on how busy you are and how much effort you have to put into each email. I recommend monthly or bi-weekly emails for freelancers who aren’t constantly producing shareable content.

Your options:

• Quarterly
• Monthly
• Bi-weekly
• Weekly
• Whenever you feel like it (Highly unrecommended. This means you’ll just never send it.)

Create an email campaign in less than an hour

Use an email newsletter service rather than sending straight from your regular email. Why? Because a) it’s free, b) it manages your list for you (automatically updating new subscribers, though you’ll have to add new clients manually), c) it has pretty templates that will make you look more professional, and d) did I mention it was free?

1. Visit Mailchimp.com and sign up for their free “entrepreneur” mail package.

It lets you send emails to up to 2,000 people, six times per month. That should take care of most of you.

I’m sure there are other services that are great too. (You can tell us about them in the comments.) But to cut on time, don’t hem and haw about which one to choose. I use Mailchimp and it’s stupid easy.

2. Use a template to create the look of your email

Upload your logo into the header. Try not to upload grainy header images -- that just looks unprofessional. Remember that a significant percentage of your email recipients may not see any photos you send. If you want to get professional, consider hiring a graphic designer to do your header.

3. Segment your subscriber list

Most newsletter services allow you to upload a list and then only send it to subscribers who meet certain criteria.

Create an excel spreadsheet of your contacts. (You can export your contacts from most email services into a .xls file.) Then create a new column based on the different types of emails you want to send. Let’s say you want to segment into “past” and “current” clients. Create a column called “Status” and put “past” or “current” in that column next to each name. Then upload into Mailchimp. Then follow the instructions on this page to send only to just past or just current clients.

4. Put a subscribe button on your website

Follow instructions here. Good for people who get link traffic through blogging. This captures people who might be interested in you or your services, but aren’t interesting in contacting you right now for a specific project.

5. Write an awesome subject line.

For tips on how to write irresistible subject lines, go here. That’s where I learned it!

6. Make sure your email is optimized for mobile.

With nearly 50% of emails being opened on mobile devices this year, it’s important that your email looks good on mobile. Mailchimp’s templates are automatically resized for mobile, but when you preview your campaign, you’ll be able to see what it will actually look like on an iPhone.

7. Always include social follow and social share buttons.

You just have to click and drag to add these buttons to your campaign. This is the most effective way to get new subscribers.

8. Invite feedback.

Ask questions. Make sure it’s clear they can respond directly to your email newsletter and get a response.

9. On the subject of photos…

Low quality images are the quickest and surest way to make yourself look unprofessional. Also, remember that only some of your subscribers will see them. So use them sparingly, make sure they weren’t taken with a 2 megapixel camera, and don’t steal other people’s copyright images off Google.

10. Send and track.

If your open rate is below 15%, you may need to rethink your subject line strategy or segment your audience by field and adapt your subject line and content to each segment. If you aren’t getting enough click throughs to your website, try bringing the links “above the fold” (so they don’t have to scroll to see them).

However, don’t obsessively focus on open rate. Even converting a few clients per year into repeat or return clients will make your email marketing program worth your time. (Plus, just seeing your name in their inbox can’t hurt you.)

Other awesome resources for email marketing

• Copyblogger (not just for bloggers, by the way)
• Content Marketing Institute
• ExactTarget’s blog
• EmailInstitute