The best advice is to ALWAYS assume the worst. If you always assume the worst then you will have a great experience.
Always assume the auctioneer is lying about ANYTHING he says about the game. Condition, price they sold for last week, what might be wrong with the game. Only exception is that if they go out of their way to tell you something bad, then you can believe that.
Assume that the first bids on an item aren't real and wait until you see actual bidding going on. Some auctioneers love to start an item at $100 and then spot $200 and $300 "bids" and then when no actual people bid they go back down to $100 again and wait for an actual bidder. Superauctions has 3 auctioneers that I know. Rob (mid 30s, brown hair) doesn't do that much, the older guy does it for almost every game, and then there is the younger muscular guy with the dark hair, who is the most straightforward of the auctioneers, but he usually only auctions things when the main auctioneer needs a break.
Assume that the working games have intermittent problems that aren't showing up that day.
Assume that the dead games have a dead power supply, dead monitor, and dead boardset.
If a game has graphics errors or boots up to garbage you should always assume it is the boardset and not the power supply.
Assume the seller of the game is bidding against you.
And the most important one. If you win a bid on a game and then all of a sudden there is some "confusion" about a bid they didn't catch or something, then just walk away. Do not raise your winning bid. Every time this happens it is because one of the auction employees (who owns the games) or insiders signalled the auctioneer that the price wasn't high enough for their liking. When that happens you are not in a fair bidding situation, you are instead letting someone who doesn't have to pay buyback or entry fees set the price that they want you to pay.