I. STIFF OUTLINES: It is one of the common mistake in sketching, where we overly draw dark outlines which looks unnatural. It’s a mistake because: 

-it makes our sketch looks like flat instead of real and 3D.

-And then if we add tones and values in sketch with this stiff outlines then it looks like a waste in it.

*for example: when sketching a tree, do not make every border dark and press to hard in all areas. The branches, leaves have different values according to lighter and darker areas.

 for natural outlines, you have to observe where the actually forms changes.

II. OVER BLENDING: Over blending means blend the shade too much that detail begins to disappear. Due to this sketch loses their texture, details and contrast. 

*for example: Think of a picture, you are making a sunset view and you over blending the color shading then its loses its realism looks flat and blurry. Instead, Blend slowly with adding layers so that it’ll look good.

So, you have to only blend where it needed, keep some areas dark, light and transparent, with which it looks more dimensional.

III. INCORRECT PROPORTONS: It means when our shape and size of our drawing is not in right size when we compare to each other. it does not match, Like imagine that you are making a face of a person and your eyes become small in compare to your nose then it looks like ‘OFF’. So, your size relationships must look match with different parts.

During sketching, it’s important to compare distance, shapes and sizes between parts.

IV. RUSHING DETAILS: When we add details in a drawing very quickly without get the basic shapes right. 

*for example: Think you are making hair of person in your drawing and without adding basics lines you directly jump into adding small details. so, first draw the basics and then add details in it. if you are always rushing in drawing then you never understand about it because, basics is what we need here first.

V. IGNORING VALUES: Ignoring values means not giving full focus on darker and lighter areas in different parts of drawing. Like, think that you start drawing an object and you don’t add light and dark in their position or you make your whole draw in lighter shades. Your draw starts look unusual.

Try not to make these same mistakes in drawing.