Huge Bargains
This is a big one you have to watch out for. Scammers often offer really low prices on items to entice people to pay for things they never intend to send. For the scammer, getting paid something is better than nothing, and for you, keeping your money is better then losing it for nothing. It's a good idea to post a buying lead requesting sellers to send you their price lists. Either that, or message several sellers that have a common product you are interested in to send you their price lists. They will send it, and you will be able to review the average wholesale price for the product you are interested in. You may notice that some sellers have prices drastically lower – like half or less than half of the average price. Instant sign of a scammer. This person will take your money and run.
Payment Methods
This is a huge red flag. Most scammers will not accept methods of payment such as Paypal, Moneybookers, LC (letter of credit), escrow service, or a reputable forwarder. Basically, a scammer doesn't want to use any form of payment method that offers the buyer any kind of security. They tend to rely on bank transfers, money grams, and western union. That's not to say a scammer won't dip into methods of payment that offer the buyer some kind of protection for a little while. They will eventually urge you to use payment methods that don't offer protection, and when you cave in, that's the week your shipment doesn't show up, and the company isn't answering emails. On the other hand, if you establish a long business relationship with a company, the other methods can be cheaper (less or no fees), and possibly faster. Any reputable company seeking more customers understands a new customer's concerns about their investment's security.
Another thing about Paypal, it doesn't offer much security outside of eBay. They still offer buyer protection, but that's only if they can recover the money. A scammer could drain the account as soon as they are paid. You would just lose your money. Scammers still stay away from Paypal often enough, simply because it isn't as easy for them to get an account in the first place. Once they pull their scam, Paypal closes their account. Paypal is much safer than wire transfers, money grams, and western union. I just want to make it perfectly clear that it isn't 100% safe, as some have been led to believe.
Testimonials and Feedback
This is the part where that language barrier that made it so difficult to negotiate price starts working in your favor. Hopefully, you didn't spend all your time sleeping in English class. Most Chinese sellers have a difficult time with the English language, and if you have a scammer on your hands, you might notice something funny about their feedback or testimonials (many sellers have a website in their contact details where they will list testimonials). They may all look the same, written in the same style, all with the same poor grammar and spelling. The seller has written their own testimonials and/or feedback. A reputable company wouldn't do this. They may be written in different styles with poor grammar and poor spelling in different places. This usually means his scammer buddies have written his testimonials and/or feedback, and he has done the same for them. Again, a reputable company wouldn't do this.
If your seller has diversified testimonials or feedback, they may be legit. Keep in mind, not everyone in the world (and they do business across the globe) is an English major. Still, there should at least be some good clean testimonials or feedback if this is truly a reputable seller.
Name Brands
There are an abundance of knock off items that are legitimately produced in China. I say legitimately, because of where they are in China, there may or may not be anything illegal about it, at least not enforced about it. They may have knockoff Nike shoes that actually do come direct from an enormous factory, just not the real Nike factories that reside in China. Sometimes, they do actually come from Nike, but they were rejects, and are therefore not licensed by Nike.
Where you're going to find problems is trying to sell those same shoes in America, where it's considered a violation of intellectual property rights. You'd be lucky if a medium like eBay or even craigslist for that matter would allow you to pass the ad through, as measures have been taken to quell infringement.
The knockoff Nikes are going to have mistakes or flaws. The average person could probably spot these flaws within a couple minutes of close inspection, and therein lies the problem. You're several thousand miles away. If you can entice your seller to allow you to inspect the product on webcam, that's wonderful, but you won't know that what the seller is letting you see is what the seller will send. The only way to know for sure is to hire a reputable agent to inspect the product for you. Could be money well spent to build a long lasting business relationship, or to dodge a financial bullet, whichever way you want to think of it. Some of the sellers are smart enough to send you a legitimate sample (such as if you only ordered one unit), and wait until you are buying in bulk to send you a box of confetti.
You can rest assure that most namebrand clothing and jewelry items listed on B2B (business to business) sites are total knockoffs. If you think you have found a seller who is selling legitimate items, it could very well be worth the effort to hire a reputable agent to inspect the items, as previously mentioned.
Longevity
Businesses are born and fold all the time, but longevity is a sign of a reputable seller. You might take a moment to see when the supplier registered with the B2B site.
On the other hand, scammers register many fake businesses on B2B sites. Their businesses are constantly removed as they are discovered as scammers. Not only should you check businesses for similarities (some of them are identical, only the names, addresses, and phone numbers are different), but you should check to see if they have been in business a relatively short amount of time. A short time in business only makes an already dodgy business look dodgier.
Another thing to consider is the so called "Gold Status" of members. All this means is that the business paid the B2B site enough money to display those icons in their ads. It's true, most of the non-gold suppliers are just scammers, but gold status doesn't necessarily mean that a supplier is honest or legitimate in any way. Keep that in mind.
It may be a good policy to use a forwarding agent no matter how much you trust the seller.