The Bay, as Dave says, is a fascinating place. It has some shark-infested waters.....which is why we always pay with a credit card. If they screw you, you can do a chargeback even months later. Don't be afraid to confront a seller who has misrepresented an item.....they are often quite prepared, even eager, to offer a partial refund to make things right.
About bidding: If you bid early you will usually contribute to raising the price because others will see the bid and far too often they have to pick away at it until they are high bidder.......then somebody else does the same for them. That's what drives the final price up.
If you bid in the last five seconds there is no time for that dynamic to occur, thus the final price will likely be far more reasonable. This is by no means assured, as snipers sometimes put in crazy bids, but if you place a smart bid, you won't get hurt.
I don't even bid if a whole bunch of people have been playing the game to be high bidder, because most auctions will be irreparably ruined by that time.
In some cases, very rarely, I will bid in such an auction if I really want a great knife, but it's usually become obvious that the final price will go too high and at some point I have to make a final careful evaluation and say no.
As far as finding the good ones goes.....that's just a matter of putting in the time and searching the many possibilities comprehensively. Look for knives that have not been described well so that searches will fail to turn them up.
Look for good knives that have not been presented accurately or intelligently to raise their profile to the collectors that would be interested in that particular and unique item.
A knife simply described as a "Buck" knife, with no model number or details which turns out, when closely examined, to be an unusual variation of a 112, is usually going to end up being a bargain.
One important thing is that if you decide to take a chance on a poorly-photographed knife from a seller that makes you a little suspicious.......remember that you are making a gamble and you're going against the odds. You might win the long shot.....usually you won't. After a while you start to get a feel for such things.