An Insiders Guide to Selling at Auctions     Vol 1

Buying at auctions can be very profitable if you know what you are doing. Really the best way to learn is to do it. Think of it a on the job training. There are different people that attend an auction for different reasons. There are those that just come for the social interaction, I call these people the "popcorn eaters". They are just there for the show. Then you the collectors or those that are there to buy to use or buy something they plan to keep. Finally, you have the traders, or dealers. These are the buyers that are there at the auction to make money. It is their job. Just like some people punch a clock or provide a service to earn a living, the traders and dealers attend auctions to buy something and turn it into a profit by reselling it. Not much different than any retail or box store really. 
Dealers and traders have different was in  which they resell. Some go auction to auction, some have a retail space, and others are strictly online sellers. This is a risky way to make a living. When you buy at auction there are no guarantees. Unlike the TV shows, it isn't always profitable and there are added expenses.

STILL SOUND EXCITING?

Know your specialty. Not everyone has a good working knowledge of the value of lots of different things. Best thing is to start out with what you like and know about. Now if your passion is heavy equipment, make sure you have a was to haul and handle this type of equipment. If you are into vintage marbles , you will just need a couple of totes and a place in your car for them.
When planning to buy at one auction and sell at another it helps to know the difference in the crowd. A matter of a few miles can make a huge difference. Get to know the market at the different places. Seasonal changes can make a difference too. It is harder to sell a lawn mower in November than it is in April. Big box stores don't have swimming pools at the end of the isle in December. Use common sense when buying out of season. An out of season item at a great price might be worth holding until the right season. 
Another thing to consider is clean up or repairs. A piece of furniture covered in dust and missing a couple of pulls bought at a low price can make a nice profit with just a good cleaning and replacing pulls. Be careful that the cost of the repairs doesn't exceed the profit potential. 
Expenses are a factor with anything. Gas, fuel, food, and lodging are just part of the expenses. Be aware of the buyers premiums and any other charges related to buying at auction including sales tax. Then think about selling the item and how much that will cost. Consignment fees, commissions, and other sellers fees should be factored in. 
Some days are better than others and you aren't always going to make money on everything. There are lots of different ways to buy and sell. No matter how you do it, whether you buy at one auction and sell at another, sell at a retail space, or sell online, it all takes thought, discipline, skill, practice, and of course a little luck.