Now girl, you know Louis Vuitton bags aren't cheap. You can break the bank buying one, because Louis Vuitton bags are only made with the best materials. Really examine the bag before you commit to making the purchase. Check to see that everything is high quality and genuine -- you can go with your instinct on this. Leather and pleather? Not hard to tell one from the other.
Get up close and personal with the logo. Louis Vuitton -- unlike many other designers -- stays symmetrical with their logo. If it's on one side of a handle, for example, it'll be on another. The logos won't vary in number and they won't disappear into the seams. Make sure they're straight and even.
Remember grade school when you matched colors and shapes? Time to bring back one of those skills. Check the colors of the handles against the colors of the piping on the bag. They should match exactly -- there won't even be a hint of variation. Varying colors? Not Louis Vuitton.
Follow the material on the bag with your finger. Louis Vuitton puts some bags together from one large piece of material. That's why one of the logos on these bags is upside down -- it flips when the fabric is wrapped. Some bags aren't made with twisted material -- both logos on the bags with separate canvas or leather on the bottom are upright. Even if your bag is made with twisted material, the pattern should match up at the seams -- unlike the time you tried to sew that polka-dot skirt. If the pattern doesn't mesh, or the logos aren't positioned correctly on the bag, then it's a knockoff. So step off.
Be suspicious if you're not getting a dust bag. Real Louis Vuitton bags come complete with a high-quality dust bag, after all. It should only say Louis Vuitton or LV on the side -- nothing else. If the material is cheap or doesn't fit the bag, says where it's been made or has any other words, or if there is even a single thread dangling from it, then you don't have a real designer bag. Say "no thank you" and spend your cash elsewhere.