how to create a clothes design and trend

many thing we must know before make design and trend:

first, we must know, the target group, who will wear this clothes.
a child, teenager, woman or man, etc, or what is their job?, a stewardess, a waiter, or what?

second, we must know how much shall the clothes cost ? ( the fabric cost, accessories cost, and the quality level), because that is impossible if we give very expensive clothes for people who just have a few money, because of that, we must adjust it.

third, what is their country weather ? lets say it's will be very funny if we make a winter jacket but we sell it in Hawai, Arab, another place that have a hot weather, our product will not sold.

Fourth, what is their cultural back ground?
the example is in indonesia, Arab, or other country that many people feel uncomfortable if they wear sexy clothes.

if we design an uniform for a company, we must know, what is the company corporate design (logo and color).

after we know all thing, than we can make a good design and our customer will like our design.