The study of product design is very important to practice hand-drawing this point, if the professional knowledge alone is good is useless, because after employment, hand-drawing will be used more.
How to practice hand-drawing is also one of the problems we suffer, many people in the profession does have a superior score, but hand-drawing is not as good as others, in employment is also a major drawback. In fact, I suggest that we can read some of the books to learn hand-drawn, many textbooks have a clear teaching, for how to achieve the accuracy of the drawn lines, as well as a variety of drawing in the wrong place has a collective explanation, hand-drawn is quite helpful.
Another is to have more practice, we can choose some works to copy, you can start from the simple, simple to practice and then bit by bit to copy the difficult, reading books is only one aspect, I think the practice is still the most can improve the level of a person's hand-drawn method. And you can also take your own hand-drawn works to their teachers or hand-drawn aspects of good students to see, so that they can point out your shortcomings, can give you some advice.
And there are a lot of videos about hand-drawing on the Internet, you can search and see how others are drawing, how to draw a straight line, how to draw a curve, how to draw a circle, etc., the gods have skills, you can learn, summarize their own drawings of the smooth way to do it. Don't be afraid to give up if you don't draw well, people always grow up in all kinds of failures and mistakes.
Anciently, a mortar and pestle can be sharpened into a needle, so as long as you insist, hand-painting can also be practiced, to have confidence in themselves. See more, practice more, learn more, find more of their own mistakes, then you will definitely make progress, any industry genius is still a minority, hard work is the shortcut for all.