Despite what some may say, auction tactics play a significant role in winning a property for a reasonable amount. It is a skill which develops with experience, so sending a friend may not always work...
Same with auction mistakes as neatly summarised by Jacque. The more experience you have the less likely you are to make mistakes and the more likely you are to spot others making them (and taking advantage of this). Emotions are a significant part of the auction game. Negotiations during auction in front of dozens of people may not be everyones cup of tee. After auction can be worse with all the smoke and mirrors...
NB: estimating what the property is worth is important but developing (prior to auction) a good feel what the property might actually sell for can be equally important.
Great post.
Leo