How do collectors establish relationships with auction houses?

The direct way is usually the easiest way. That is: buy and sell art.

Are auction houses required to have certificates of authenticity to accompany their art consignments? Shouldn't this be required to save buyers from fraud and deception and getting fakes? What's the best practice

Why do people buy celebrity garbage/trash/throwaways at auction? - Quora

What does it take for an artist to have their works listed on prestigious auction houses like Christie's or Sotheby's? - Quora

I am downsizing our personal Hollywood collection, with a rare film print just found of 'This is Cinerama'. How do I confirm and value it for auction? - Quora

Are auction houses required to have certificates of authenticity to accompany their art consignments? Shouldn't this be required to save buyers from fraud and deception and getting fakes? What's the best practice

How do auction houses work? - Quora

What is the record for the highest selling price of a camera at an auction house like Sotheby's or Christie's? - Quora

What does it take for an artist to have their works listed on prestigious auction houses like Christie's or Sotheby's? - Quora

Why do auction houses sell sensitive items like Michael Jackson's stolen studio tapes even when their legality is in question? - Quora

What role do you think auction houses play in preventing the sale of counterfeit items in their auctions? - Quora

What happens to the royal family's old stuff? Do they auction it off or sell it to museums? - Quora