Sometimes mass-produced clothing doesn't have the same personality or shape that something custom made would have. China is known for its tailors and custom-made clothing, but you don't even have to be in China to get it done. Some tailors offer their services online and ship around the world. This is especially true of tailors who make or specialize in dress shirts for men and women.
Do your research. Check on forums to see which tailors are most recommended and how long it will take for your shirt to be made and delivered. Different tailors have different reputations, and some may be more reliable or faster than others.
Take your measurements. Have a friend assist you when doing this, if possible. When ordering, the tailors' website will often provide you with a diagram of the measurements needed. Chest, wrist, arm length, waist and neck measurements are the most common.
Choose your fabric. If going in person to a tailor, they will provide you with a book full of fabric swatches from which to choose. If doing it online, it may be a little more difficult. Read up on the different consistencies of fabric to get a real sense before choosing what you'd like.
Choose your details. While you may not think many elements go into a shirt, pants or suit, there are details like the type of collar, cut or cuffs to choose from. Some tailors will offer photographs of the options online or samples of their work in their stores.
Place your order and make sure to check in frequently.