Let's see the fifth tip ...

5. Every single affiliate link should be set as nofollow

First of all, let's define the term itself.

When the search engine bots are crawling your content, they will also "follow" the destination pages of your outgoing hyperlinks, in order to build your link profile and to calculate your organic link authority.

Now the thing is that by default all the hyperlinks are dofollow. In other words, Google will (would) follow your affiliate links to.

Which is not a good thing ...

Why? Because for search engines your affiliate links are a means of earning affiliate commissions, therefore these links are far from being a natural authority signal.

This is why is a mandatory basic requirement to use the nofollow attribute for all your affiliate links.

The truth is that nowadays the search engines are smart enough to recognize the most popular affiliate platforms in order to "automatically" nofollow the involved links, but that''s a different story. YOU need to use the nofollow tag for your affiliate links, especially if you are pointing to less popular networks or websites.

Also, consistently nofollowing your affiliate links, spares you the concern of being penalized for doorway pages which pass all of their traffic to a different website.