You need a dealers license or know someone who has one. There are guys on Craigslist with licenses, willing to take people to the auctions to inspect the cars and bid on them. They charge anywhere from $200-500 per transaction.
If you take this route, make sure you do all of the due diligence yourself. Even though most of these cars are “Guaranteed,” they still might be lemons or have undisclosed issues. And even through there’s Arbitration through Mannheim, if the car has problems, no dealer/broker will go through the hassle of Are for a mere $500 - so you may be stuck with the car. MAKE SURE YOU DO YOUR DUE DILIGENCE.
And, even though most of these auctions are on consignment for the dealer. You’ll need to have cash to pay. If he trusts you, he may give you a day or arrange financing himself. NEVER PAY HIM UPFRONT. If you need to finance the buy, get pre-approved with your credit union and be ready to close after the auction.
Also, auction houses are small communities, everyone knows each other, so when newbies come to bid on cars they usually get suckered into over bidding. These folks are sharks, evaluate the landscape before committing to bids.