Auctions sell property at a specific time and place to the highest bidder. Most auctions require a person to get a bidder number or other identifying item prior to bidding.
If you're selling something: Why choose an auction over other sales? An auction gathers people who are looking specifically for the item being sold, and the more people you have at an auction, the better chances of getting good prices. When you have two or more people competing for the same item, the price usually goes up.
If you're buying something: Live auctions can be fun. Most auctions run on a number system for bidding. You'll get a number, usually written on a card. When you win a bid, the auctioneer will want to know your number. It's easiest to bid by raising the card, but at least have the card ready.
For most auctions, you can start looking at items at least one or two hours before the auction starts. Auction houses often have a preview the day before the auction. The more time you have to look at things, the better. Take a notebook/pen, a decent small magnifying glass, and a digital camera. Never bid on an item you haven't looked at!
There are bargains at almost every auction. You just have to recognize it and decide whether or not it's something you want. While auctions increase the competition, they also increase the odds that something will slip through at a bargain.