Create an Email List
Whether you are an affiliate marketer, the owner of an e-commerce store or you are promoting and selling your own product, you should be using a funnel that moves visitors from visitor to prospect to customer.
An essential part of that process is to get their name and email address as early in the process as possible. In other words, create an email list.
Then you have a list of customers and prospective customers. If they didn't buy your product or your vendor's product, you have another chance to persuade them with a better offer or simply more convincing factors. If they did buy, you have the chance to sell them additional products, related or alternative. Remember, it's always easier to sell to someone who's already bought from you previously.
The Money is in the List

How many times have you heard that?
It's totally and absolutely true.
If you have a monetized website, you must create a list of customers and their email addresses so that you can email them again with new offers. An existing customer is 90% more likely to buy from you than a new prospect.
An existing customer is the only person you can request a testimonial from. And testimonials are your best weapon for building trust.
And, unless you're dropshipping or selling your own product (which pretty much means you're an affiliate marketer) your list is your only asset if/when you want to sell your business.
All you need in your list is your customer's name (even just their first name) and their email address. But how do you get them and where do you store them? This takes us into the wonderful world of opt-ins, landing pages and autoresponders. All will be revealed in this article.
But I'm an Affiliate Marketer (You Still Need to Create an Email List)

It's the big downside of affiliate marketing.
You spend time, money or both promoting a vendor's offer.
Some of your visitors click on your link, buy the product you're promoting and you get paid an affiliate commission.
Who collects that customer's name and email address? Your vendor, not you.
But it's your customer.
You spent time, money and effort (probably all three) in acquiring that customer. Don't you deserve to know who they are? And to have their name and email address details so that you can build up a loyal tribe who will buy from you over and over again. That's what internet marketing is all about!
How Valuable are the Customer's Contact Details?
Here's an example: I have a vendor whose products I promote. One of those products sells for $69 and I get an affiliate commission of $120! Read that again. I get (considerably) more in commission than the vendor gets from the sale. That's how valuable this vendor sees their customer's contact details. Because they can sell to them over and over again.
The best set of tools available to do all of this easily are found in the Thrive Suite. And if you want to learn all about affiliate marketing and building a website your best resource is Wealthy Affiliate, which you can join for free. Learn how you can qualify to have me build your first website for you at no cost. Just click on Wealthy Affiliate to find out more.
How to Collect YOUR Customer's Details and Create an Email List
Note the emphasis on "your". You are the one who's spent time and money acquiring the customer. They are your customer and you are entitled to know who they are! To collect your customer's detail, you need 1) a Lead Generation form and 2) an autoresponder that allows you to keep your customer's name and email address on file and stay in contact with them. You also need to understand Landing Pages.

Lead Generation Form
There are plugins that allow you to add a Lead Generation form to a page on your WordPress website. The plugin will produce a form that asks the visitor to fill in their details. Keep the requested fields to a minimum, perhaps just First Name and Email Address. You will get more sign-ups that way. Search for "WordPress lead generation forms" and research what comes up. Some are free, some are paid and some are free with a paid upgrade. None are expensive. You could check out 12 Best Lead Generation WordPress Plugins from WPBeginner for starters. However, the Thrive Suite contains a large selection of Lead Generation forms that you can simply drag and drop onto your WordPress page or post.
Autoresponder
There are several autoresponders to choose from AWeber and GetResponse have been around the longest. MailChimp has a free plan that you upgrade when your list exceeds a certain number. I use Active Campaign because I like its User Interface and it allows me to create more complex automations. It also has an excellent delivery rate. Do your research and choose one that suits your style. All have export/import facilities that allow you to swap from one to another. You will link your Lead Generation form to your autoresponder using the built-in facilities provided by your form. Typically, you will create an automation in your autoresponder that sends a welcoming email to anyone who signs up using your form.
Why Should Anyone Fill in My Form?
All of this begs the question: Why should anyone fill in my form? Which brings us to two new concepts. Landing pages and opt-ins/giveaways/bribes. You persuade your visitor to give you their name and email address in exchange for a free gift. And landing pages are what you use to bring the offer to their attention and to follow it through. Let me explain.
But I Haven't Got a Free Gift

You can't really do flowers and chocolate (best save them for Valentine's Day) and they're not very downloadable, but creating a free gift is easier than you might think.
You use PLR (Private Label Rights) that's relevant to your niche.
Just search [niche] PLR and you should find plenty to choose from. They are typically books and cost just a few dollars. You are allowed to claim authorship and change the cover if you have the tools to do so.
For example, here's one of mine in the Pets niche:

Emma Morgan is my collaborator on this site, so I used her name as the author (there's one for dog training as well which has my name).
I think the PLR cost me around $7. It came with a cover (which I've replaced) and in both PDF and Word formats. I made some changes in the Word file, used my own template and recreated it as a PDF. Around an hour's work all up.
The template I used is the Word doc I initially created for books that I publish on Amazon via KDP.
It uses one of KDP's preferred sizes (9" x 6") and follows a standard format of Title (and optional sub-title) page, disclaimer and contact link, table of contents, content and a link to find other books. Fonts for chapter heading, headings, paragraphs and drop caps are all pre-set and images are set up to fit between the margins.
So all I have to do with a PLR is copy the content and paste it into the template to have a fully formatted book. Then proof read it and fix any grammatical and spelling errors. I might do a bit of rewriting as well. I'd have to do a serious rewrite if I wanted to publish on Amazon, of course, but the Word doc is ready to be published as a Kindle. Save it as a PDF and it's ready to be published as a paperback as well.
Landing Pages Help to Create an Email List
Landing pages are just pages on your website that you aim to get visitors to land on and take some action, such as linking to a vendor's site through your affiliate link or, as in this case, offering them a gift in exchange for their name and email address.
Often, a landing page doesn't include your menus, so that the visitor's only choice is to take the required action or leave, but this isn't essential.
You promote the landing page through blog posts or advertising.
This opt-in/lead generation requires three landing pages:
1. Gift. This page discusses why the visitor needs this free gift (and, of course, includes an illustration like the one shown above) and provides the lead generation form for them to enter their details in order to get it.
2. Gift Confirmation. The visitor sees this page immediately after they submit their details. It tells them that an email has been sent to the address they entered with a link to download the gift. At the same time, your autoresponder has sent them this email.
Note that this protects you against someone entering a fake email address.
3. Gift Download. This is the page linked to in the email. It contains the link to the gift itself, usually a PDF that has been compressed into a Zip file.
Conclusion
At the end of this process, your visitor has a gift and you have their details on your mailing list.
Your autoresponder should be set up to send them a second email fairly quickly (like maybe a couple of hours after the initial one) with a link to another landing page.
This landing page will pre-sell an affiliate product closely related to their free gift and containing your affiliate link.
Repeat for different (but all related) products.
Rinse and repeat the whole process.
I hope you found this useful to help you create an email list. Don't hesitate to respond if you have any questions about this process.
You can also pick up my free book The 4 Things You Must Know (to make money while you sleep).
And for the complete kickstart to your online business, checkout Wealthy Affiliate and Thrive Suite.
See also
https://superaffiliatechallenge.com/how-to-start-an-online-business-for-free/
https://superaffiliatechallenge.com/hey-wordpress-whats-on-the-menu/
https://superaffiliatechallenge.com/motivation-gets-you-started-habit-keeps-you-going/