First, you buy the seller. If their reputation and feedback from various sources make it appear he's decent, then he could be. I've got stung twice by that, tho, one from a auction vendor who dropped off the face of earth after 1,000 sales, another by a forum member at TOS who "just changed his mind." And did nothing to communicate that. You have to accept the risk of human behavior. One poor guy was hit in a traffic accident, and it took months to clear up the issue. No one in the family had a clue to check his transactions, it took a forum member in that city to track things down. So, things happen. Planes and ships sink, the USPS finds your parcel 30 years later. There is no absolute guarantee.
Then check the merchandise. The use of stock photos is problematic. They may very well depict a brand new knife in the box, and the vendor has dozens. Individual pictures taken every time would be redundant and unnecessary. A used or unique knife, tho, should be all original content. And the pics need to match the description - hosting a stock photo of the left and right views of a knife, plain edge, and describing it as serrated is careless. It's a flag to look further, even question the seller. I have, I got a surly response. The use of pics other than your own is a hot button issue on auction forums.
That description needs to be accurate, and should be biased toward the buyer. That doesn't always happen, most sellers like to describe an item in glowing terms, what they leave out is the important stuff. "Lightly carried and used" might be interpreted from one extreme to another, but generally, the edge should be barely touched up. Reshaping it on a bench grinder would be too much, tho, but sometimes little facts like that are omitted. So, the conditions are only a general guideline. "New in box, mint" could still have assembly dings or scratches in hard to see locations, or even right out on the blade. It happens - shipped from the factory.
After all that, consider the site. Most fakes are sold in the largest mass communication possible, to catch the eye of the unknowledgeable. That's where someone who wants to the look but who won't understand the quality details will be visiting, and where impulse purchasing is most likely. There are dozens of models coming out of China right now, look alikes for all the high end folders on the market, for less than 25% of the cost. The rule there is you get what you pay for. A Strider SnG copy for $75 is still a huge profit for them, and there seem to be plenty lined up to buy, just like fake Rolexes with cheap quartz movements. All too many want image instead of depth of character, and there are plenty of other humans willing to take their money and enable their fantasy.
Learning the ins and outs means being in a position to listen to those with the experience, likely because it cost them dearly. Those lessons are free, it's a matter of sorting out why they are saying it. In gun and knife forums, however, there is an element who are more reactive than thoughtful, and their interest is more oriented to preserving their social status. Things will quickly deteriorate into a measuring contest if dogma isn't instantly accepted. Avoid them. What the experts say is that the more they know, the more they don't know it all.
Don't fixate on one type of knife - after 40 years of messing around with them, new interests come up, and some old itches get scratched well enough that the particular interest is fulfilled for years, all because one model really does it all for you. I've searche for the best 3 1/2" tactical folder since 1984, and have some good ones. Presently, I'm playing with sub 2" fixed knives - who knew? As life changes, so do your interests.
And don't worry about the fakes too much, I've got a scar from them, too. Not so fake after all.
