You can't really put yourself into bankruptcy buying a million dollar antique at an auction by absentmindedly scratching an eyebrow. It can actually be quite hard to attract attention, and an eyebrow scratch should only signal a bid if you've prearranged it with the auctioneer. If there's a doubt, the auctioneer will ask you.
Lots of people are timid about - or downright scared of - bidding at live auctions, and there's no need to be.
Find out why in our (easy to read, I hope) 'How to' auction essay.