How to bid intelligently at an auction

Or at least how to pay an appropriate amount for an item:

Research any advertised big-ticket items. Know what they should cost new or used so that you don't overbid once the chant starts.
Check out the goods beforehand. Once the auction starts, things will move fast and the item you want could be sold in the first five minutes.
Go easy your first few auctions. The deals are fantastic. Just show some restraint or you'll have a garage full of stuff.
Learn whether the auctioneer starts high or low. If they start high, they'll work their way down until someone bites. If you're the first one to bite, make sure you'll get a great deal.
Be clear when you bid. If you half-raise your hand in anticipation that another box will be added to that $5 lot, you may just get in your bid before that box is added. Oops.
Make sure you know what lot is up for bid. Bid on the one you want, not the one you don't want!
Watch like a hawk. Someone could have moved your item to a different box. It could get piled in with a number of other box lots that wouldn't sell by themselves.
Call out your price if it's not going down fast enough. The worst that can happen is that they'll say no.
Split the difference on a bid if you want. If someone else has bid $15, and the auctioneer is asking $20, offer to bid $17.50. Again, the worst they can say is no.
The second bid may be the clincher. This happened to me. I was first bidder on several items and I got outbid every time. After I bid second, outbidding the person who started at the price I had begun at on the other auctions, I won a few of them.
Bring cash or check if possible. There will often be a cash discount or a reduced buyer's premium.
Speaking of buyer's premium, factor that into your bid, as well as any sales tax.
The auctioneer is a charmer. So watch out about becoming a snake. Hand gestures, eye contact, urgency, teasing, and scolding are all tricks that auctioneers use to get you to bid more. Resistance is not futile.