We look at many factors to be able to offer our clients the best quality links. First off, we look out how well the site is being managed. We make sure they are creating well written articles and are publishing a blog post at a consistent interval without spammy tactics. We also have many API’s that lets us review the site’s metrics in order to determine how strong the site is from a link standpoint.
For instance- we look at Moz ”domain authority”, Majestic “trust flow”, and Ahrefs “Domain Rating” just to name a few. This gives a full picture view of the site, and makes it easy to decide if the site is a good fit for any of our clients. We also love sites with good social media presence.