Often do sketches
Sketch is a particular way of quick-drawing. Also referred to as collage, especially in the word of fashion sketching differs from proper drawing. It’s more of a basic description of an idea, which will either be elaborated on or not. Being basic will not make any sketch worthless or less valued than a complete artwork. Just check out all the hysteria which ensues as often as sketches of famous artists are found by accident at some flea markets or in some sketchbooks.
First of all, learn how to sketch your own way. Everyone needs to grasp some basic knowledge in order to do a good quality sketch (remember, simple stick-figures are not sketches) then you can go ahead and improve until the point you feel that you have confidently found your own sketching style. Once you are good enough, you will realize that you will be able to draw a sketch within one or two minutes only.