Figure 1: Fake vs Real Louis Vuitton Speedy handbag
[SHAPE] The Speedy bag on the right hand side is the authentic Louis Vuitton. When directly compared to the fake Speedy bag on the left, the superior, well defined shape of the authentic bag is quite clear. Authentic Louis Vuitton handbags (and other items) will have well defined shapes and lines. All of which is evidence of the world-class quality and craftsmanship. On the other hand, the fakes will often times lose form, having an undefined shape. Somewhat like the before and after photos of late night workout video infomercials. (The fake representing the before photo, and the authentic representing the after).
(i) Also notice the color of the symbols in the fake compared to the authentic.
Figure 2: Authentic snap
[HARDWARE] The snap in Figure 2 illustrates the aged (bronze/matte) look of the hardware generally found on authentic Louis Vuitton. This is also a common theme across the majority of the high end designers. Counterfeiters will often utilize lower quality hardware that generally has a distinct glossy gold shimmer. This is not to say that Louis Vuitton does not manufacture items with polished metals, but rather always make sure if the authentic model utilizes the matte or the polished hardware. Polished hardware on an item that is supposed to be fixed with matte (or vice versa) would be a signature of a counterfeit.
Figure 2.1: Counterfeit screw
[Fake] An authentic Louis Vuitton hardware screw mechanism will not be the 'Phillips-head' ( + ) variety. Instead, you should expect to see flat head screws ( - ). The example on the left hand side is a Phillips head screw. This is an instant signature of a counterfeit.
Figure 3-4: Louis Vuitton seam lines
[STITCHING] Figures 3-4 demonstrate the quality of the Louis Vuitton stitch (seam) lines. They should not appear sloppy, or appear to have been rushed. Also notice in Figure 4 the texture of the stitch. There ridges indicate that this is a higher quality material. Comparing the number of stitches per inch (SPI) is also a crucial counterfeit spotting tool. Authentic high-end items often have more stitches per inch than the counterfeit items. 
Figure 5: Fake_Louis Vuitton stitch line
[Figure 5] is an example of a sloppy stitch line found in a fake LV handbag. Often times these counterfeit stitching signatures will be found inside the handbag, and not on exterior areas. The reason is that the counterfeiters (correctly) assume that most people will not sufficiently inspect the interior seam lines. Therefore the rushed, sloppy work will be out of plain site. However, always take the time to go through the interior of the Louis Vuitton handbag and look for these problems.