No Product Testing
"One of the biggest mistakes I've made was not doing my own shrinkage tests. What they don't tell you when you first start out is that the same jersey or fleece knit can and will shrink differently based on the color it's been dyed, and/or the lot it comes from. Making matters worse is if you're getting your fabrics from a jobber [Ed note: the middle man charging "discount" prices], 'cause they'll send whatever they have, not necessarily what you ordered. I learned this the hard way my second season out.
"For my first run of sweats, I used an 80/20 cotton poly fleece. When I reordered, I was sent a 95/5, but I was told it was the same 80/20. So, I did the run, and what do you know, I ended up with sweatshirts much shorter then the first round due to the higher cotton content. Luckily, most of my business was in Japan at the time, and they already thought my sweats were too long, so it worked out okay. But, moral of the story is never trust jobbers—they all lie—and always check your fabric shrinkage on your own before doing a production run, or prepare to pull out a lot of hair, and lose a lot of money."