I have been buying at auctions most of my life. IMHO, they can be the best or the worst way to buy something. I depends on a many variables but mainly on the buyers, skills. I have gotten great deals and I have learned some tough lessons...
The number one rule: Carefully set your maximum bid and never, ever bid over it. It's very easy to get sucked into the "heat of battle" that preys on your competitiveness, the bidding becomes more about winning and ego, than the actual cost of the item. Fall into that trap and your are done, your wallet will be picked clean.
Carefully inspect the item. It's best done in person but if only by photos, be carful not to be swayed by secondary information. EG. Let's say the lot item is a cabinet full of tooling, you can see various tools but there's also box that is labeled "X valuable tool" Don't assume tool x is in the box, only consider what you actually see. Add up the maximum real value of the item(s) subtract the sum of all premiums, fees, taxes, etc. That is your maximum bid amount. Also don't forget to consider the cost of travel expenses, rigging, etc.
Patience is key, if you didn't win at this auction you might at the next. Play the long game, eventually you'll score.