To bid in California, you need to qualify. In most states, qualifying requires showing the auctioneer your identification, and cash or a cashiers check sufficient to cover the full amount you wish to bid.
Most investors take cashiers checks made out to themselves. This way, if you are not the winning bidder, you can easily redeposit the funds. And if you are the winning bidder, you can endorse the check over to the trustee. However, trustees can have their own payment requirements.