Let's start with the collar: The collar for the Qipao goes all the way from chest to the neck, kind of like a "turtle neck" but much more elegant. If you have a beautiful long, thin neck it's perfect. But if your neck is not that beautiful or a little short, you can ask to make the collar not so long, and make the V part a little deeper.
Sleeves is a very important part of the Qipao. If you have long elegant arms, just have them shown outside of the Qipao. If your arms are slim but not so long, begin the cut from the shoulder. However, if they are a little big, you can choose Qipao with sleeves. (I've seen some women wearing Qipao wih their huge arms outside, and I lost appetite for the whole dinner.) The length of the sleeves helps a lot for the whole impression. If you have smaller shoulder, make the sleeves very short (this doesn’t go with women with big arms). If you have very big shoulder, the 1/2 sleeves may fit you better.
There’re two cuts on the both side of your leg. I recommend the length to be half of your thigh. Because when the cut is too deep, you will make yourself an entertaining street girl in China. If it’s too less, it makes your leg look short.
Don’t just choose whatever color you like, choose the color which really goes with you. Many people think the traditional color is red, so they would buy a completely red Qipao, but they didn’t know red Qipao is especially for weddings in China. Many women love pink, but don’t go for that unless you are extremely thin, or if you want to look like the cute round “hello kitty”. Choose a Qipao with intensive color combination. Black, red and gold is my favorite. Red and green is very special, too. Purple and yellow, blue and white… Oh yeah, a woman can never have enough Qipao!