How do I draw a pansy leaf?

Find a reference photo online from a good source. Sketch the basic shape. Ignore any bumps or veins. If you're drawing the stem too, just draw a line in the shape you want the stem to be. Find patterns. This is stuff like how many bumps are on each side or how the main veins fit together. Fill in the details. Draw the shape of the stem around your original line. Pay attention to thickness and if the bottom is straight, like it was cut, or curved, like it was plucked off the main stem of the plant. Pick a light source for shading. Remember that light comes from there and only there.