Keys to accurate drawings:
If you can't put a name to the object you are drawing, it's not likely that your mind will predetermine how that object should look in a drawing. Below are two exercises that will help you banish pre-conceived ideas while you observe and draw.
Begin by drawing two squares with the sides of at least 3 inches, (7.6 cm) long. Squares that are much smaller than this will cramp your work space. Keep in mind that teeny tiny drawings allow the creation of teeny tiny errors, which are much harder to see and correct.
Working within a square will provide vertical and horizontal boundary lines for making comparisons. As you observe the shapes within the square's perimeter, ask yourself these questions:
How close to the perimeter is each shape?
How do the angles formed by the shapes compare to vertical and horizontal?
Do the shapes cross through the center of the swaure and if so, by how much?
How does each shape compare in size to ther others around it?
What do the empty spaces surrounding the shapes look like and how large are they?
Making these comparisons will help you see the subject in a anew, more comprehensive way. now, try to draw the shapes in the boxes with as much accuracy as you can.