Drawing, sculpting, modeling, and texturing require an extra keen sense of observation. Seeing is the primary skill to develop in order to become a good draftsman. It's not about the pen or paper you use. It's not about Maya or Max; it's about your own ability to seize the truth about an object with top-notch precision.
When a 3D modeler is given a concept art, she needs to be sensitive enough to grasp the subtleties of the design and the character behind it. Often it's very difficult to turn a gestural speed painting into a 3D object. The key here is not to do a simple translation 2D to 3D. It's to re-create/re-interpret in 3D the gesture proposed in the 2D concept art. It's like listening to an interpretation of your favorite heavy metal band by a philharmonic orchestra. The two versions will sound very different, but both will vibrate the same energy if executed skillfully.
Artists look into evaluating shapes, volumes, their relations to each other, the pattern of the positive and negative space, their surface. We also look at the character of things, their age, wear, sturdiness or fragility, their stories. We need to select only the essential information. It's caricaturing on the go -- leaving out information that doesn't matter to focus on the truth. Become expert at oozing out the essence of things.
Seeing is not about being able to create a photorealistic drawing of an object. Art is not interested in duplication. Art in entertainment should be bigger than life. Art needs exaggeration in order to be convincing and entertaining. If your art direction calls for something dull, then you need to create duller than life. It work both ways; the nice becomes nicer, and the ugly gets... uglier.
From time to time in applicants' portfolios, I see highly realistic renderings of famous people done in pencil from photographs. If you're not at least as fast as a photocopy machine, it won't be impressive. I will always prefer a three-line drawing capturing the likeness of someone. I know that person has a keen sense of observation and is capable with very few lines of expressing ideas, feelings, or stories. Again, it doesn't matter which medium you use, whether it's an expensive 3D software package or a lost twig on the beach.
It comes down to observation. One way to practice your observation skill is to draw anything, anytime, all the time. Carry a sketchbook with you. Whenever you have five minutes to kill, commuting, at the bank, or sitting for a coffee, pull out your pencil and notepad, and draw something that is around you. It could be people; it could be an object. You sole focus is essence. You want to simplify some shapes, you want to exaggerate some others, and your personal style is defined by what you leave out versus what you keep in, crowned by what you add.
Here are two delightful drawings by Matt Jones. I really enjoy the way he depicts the city. The details he chose, ignored, enhanced, and weakened made his drawings more San Francisco than San Francisco itself.
If you study life drawing, don't focus solely on anatomy; go for a story. Extrapolate, exaggerate, twist reality. This is how great drawings are achieved. Don't reduce yourself to the capacity of a camera. Be the artist you ought to be.
There is a popular belief that goes, "I don't need to know how to draw, because I work in 3D." To that I would say, "Maybe. But why on Earth would you limit yourself?" The ability to draw is proof of your mental visualization and observation power. Many people think drawing happens between your finger and your pencil, but in fact drawing happens in your brain, using your ability to visualize something with extreme clarity.
If you have enough dexterity to hold a pen to write down your name, you possess enough dexterity to draw like most of the masters. The difference between you and them is the power of your observational skill. From my experience, the top performers in my teams were often good draftsmen. Not always, but they had the upper hand in speed of execution, quality of shapes, texturing, and concept art reading.
In the mid '90s, stricken by illness, Frank Frazetta couldn't rely on his right hand anymore. He started to train his left hand by drawing and painting. After few months, he was able to create some very decent pieces of art. Some critics even say that his drawing actually improved. Well, I don't know about that, but he drew skillfully with his non-dominant hand after a relatively short period of time.
My point here, again, is about the required dexterity to draw and paint. Because Frazetta already knew how to paint and draw in his head, it was only a matter of making his left hand as agile as his right. "Only" is an understatement; it still takes effort to get the brain to wire new neural connections. It must have required great patience of him, but he did it. At that point, his right hand had more than 50 years of experience in drawing and painting.
Another thing I could add about drawing is that it never gets easier with time or experience. It remains hard. It is not an automated task, like running or driving a car. Your drawings will become better over time. You'll gain confidence. The difficulty, however, will remain the same.
The goals you set for yourself will rise with your skills... all your life. Have you ever noticed how artists will often diminish their work in public? They'll only see "errors" they think they could have done better. Hence the saying "a piece of art is never quite completed."
Tricks and formulas are to be ignored; leave shortcuts to amateurs. When learning to draw, you want the real deal. It will be hard, but once the skill of draftsmanship envelops you like a second skin, you'll be free to express whatever you want to say. Tricks and formulas can't give you such freedom. They will work only for a tiny speck of possibilities.
For great artistry, you want freedom to make statements. The freedom to draw, sculpt or paint the views you have in mind. Your main concern should not be how to draw, but what to draw. Stop drawing three-fourths angle portraits because it's the only way you can draw a nose properly. Free yourself from that angle by learning to represent a nose in multiple angles. Stop drawing clenched fists; draw the full hands and let them participate in the story you are depicting. Stop hiding the character's feet in tall grass. Learn to draw feet, shoes, and boots in all possible angles. Try not to avoid what you consider your weaknesses; confront them.
Don't be afraid to use reference when possible. It's a clever way of working, assuming that you're not bluntly copying. A reference should give you some basic information about an object, an environment, a mood, or a character. You need to twist that information using your art fundamentals and the vision you're trying to achieve. You need to mold that reference to match your personal statement.
Don't think it all needs to come from your head. You have to have documents; don't assume good draftsmen draw everything from memory. They don't. Many use references. Hugo Pratt spent countless hours in libraries for his research for Corto Maltese. Norman Rockwell used models and photographic references for his masterpieces. Why is it perceived as a weakness to use references? How realistic is the expectation that one should know everything and draw from his head?