Drawing accurately is based on observation. You are about to interpret a 3 dimensional view onto essentially a flat surface. There are other kinds of 'flat' surfaces like drawing on a ceramic bowl or a multi-faceted polygon, but the seeing process is similar. To observe in drawing terms is to get to know your subject. Observing a leaf is knowing that there are such things a patterns, texture and shapes that make a particular leaf different from another.
Understanding any shape is to observe that it relies on a set of references. A leaf's position relies on it's relationship to the edges of our drawing page. If the leaf is parallel to the vertical edges we accept it's position as being 'upright.' A shape i
s 'large' when seen in relation to smaller shapes. A shaded area is dark against a light background and vice-versa. And when it's placed next to an even darker area it appears lighter. As the saying goes, 'it's all relative.'
Drawing is a seeing process and not an exclusive province of 'talented' people. At whatever level, drawing makes people see more, remember more; a way of observing that translates into many areas of our lives. The physical world is filled with textures, shapes, and all kinds of surface properties. It enriches the experience and puts an added level of awareness in our day to day lives.