I have bought tens of cars from auctions
First go with someone who knows cars ,get there in plenty of time choose the car/s you are interested in try not to pick too close lot numbers -why ,later -
never buy a car that you haven't heard start because it might need a battery ,which means you have a problem straight away getting it home ,then before it starts check that the engine was cold as you might see blue smoke from the exhaust ,thats bad -but not the normal fumes they are ok
get down and look underneath for obvious rust around the suspension and edges of the bodywork
grab hold of the front wheels and try the rattle them from side to side then up and down to see if there is any movement or knocks check the windows for signs of leaks inside , check that the doors are fine by trying to lift them whilst they are open ,look down the sides of the car from the front and back both sides ,this will tell you if anything is out of line .Go as far away from the car as you can and see it is sitting properly not too high front or back and if you think it is fine
Then
you get a second hand guide that gives auction prices rated by the mileage and this is your guide price
Now the nervous bit
After the car starts and you happy go near to where the car will be when the auctioneer takes the bids and watch ,you know what you want to pay DO NOT GO OVER IT EVER but don't bid the auctioneer will offer the final bid THREE times if it is lower than you want to pay by a long way ,then this car has probably been in before and all the dealers know it and wont bid
if it is quite near then just before the final offer raise your hand for the auctioneer to accept your bid and then turn away you will hear if you won it
But dont bid more than once as some people make a good living from the many tricks played in an auction such as taking bids off the wall which means if you stand there with your hand high for to long the auctioneer just might take a bid of the wall and then a further bid from you and you will be asked to pay a higher price than was necessary and remember it is better to have lost than to have bought a baddun
So dont get into a bidding war because it happens so fast and it just might be the owner you are bidding against !
the price you should have paid then should be an insurance in case you have bought a problem compared with what you would have paid from a dealer
Lastly it is really good if you are not in a rush to go for a few visits to the same and other local auctions to get to know what is going around and are the auction guide prices accurate for your area and to see if your dream car is coming up time and again ,because some cars are bought and sold again the same week because they are found to have a problem
Lastly don't trust the really nice guy who just happens to be at the car and says it is a really nice one but not the kind he is looking for -he could be the owner
As I said I have bought most of my 49 cars from auctions and YES I have bought a couple of duds but I have bought some crackers as well
Good luck