sorry my English is not so good.
1>draw the shape and fill color (make sure 100% fill)
2>draw the leaf vein by brush tool. If not sure, google some reference picture.
3>add color layer. Use brush to make some leaf shape for background, add Gaussian Blur filter.
4>When sun light shine on leaf, it make a yellow color, not just light green.
5>add some water drops and environment light.