The BIG TWO

Ralph Lauren & Nike are two of the most searched and sought after American brands on ebay.  Thus, if you can find the right items from these brands at the right price, there is money to be made, and lots of it.
It's not as simple as 'if you see an item at 75% off buy it'.  Some items are in such high demand, if purchased at retail you can make 100-300% profit on them, but other items may not bring 10% of their retail price when on an online auction.  The key is to familiarize yourself enough with the items (style codes, where to find item identifiers, etc) so that with a smart phone and a little bit of research, in a matter of seconds anyone can know whether a 'deal' is a score or not worth the risk.

Ex.
A few months back I started seeing a few pairs of these Ralph Lauren sunglasses at TJ Maxx.
Whereas most RL sunglasses at TJ Maxx / Marshalls are $19.99-$39.99, these were $79.99.  The reason being, these are RL Purple Label, the luxury 'made it italy' subdivision of Ralph Lauren. Comparing them to other RL sunglasses, the quality is clearly of a higher level and the 'Ralph Lauren' sticker in cursive script is a Purple Label giveaway.  But, if you're not familiar with Purple Label, identifying these is as simple as looking on the inside arm of the sunglasses.  There you will see the 'PL' (designating Purple Label, vs RL or PS...polo sport) and then the style code, 9763 5089/53.
With a quick google search of 'Ralph Lauren 9763 sunglasses'