The best link building covers a range of different types of links, including guest posts, brand mentions, unlinked mentions, PR, social media mentions, and other off-page signals. That being said, when it comes to link building, I focus mainly on authoritative websites that are trusted by Google and other search engines and are receiving traffic. Although I do take metrics like domain authority, domain rating, page authority, citation flow/trust flow, and others into account, the main focus is on real websites with real visitors where a link would add real value to users.