The first thing you need to know about auctions and trades is: ALWAYS LOOK FOR THE LOWEST DEAL. It may seem obvious, but sometimes the right trade slips right by, so keep your eyes open!!!
To go to auctions now. The best way to bid on an auction is to bid on a “ghost auction”. These auctions have 5 or less bids every hour. Personally, I bid ONLY when the amount of time left in the auction is <30 minutes because you have a better chance of getting it then.
If you are the one MAKING the auction, here are some helpful hints. First of all, make sure you check the auctions BEFORE you make it, so you can set the first price lower than all of the other prices. make the minimum increment at most 3% of the original price. In other words, if the item you are auctioning is 800 neopoints, make sure you make the minimum increment under 100 neopoints.