  In this paper, we obtain coefficient criteria for a normalized harmonic
function defined in the unit disk to be close-to-convex and fully starlike,
respectively. Using these coefficient conditions, we present different classes
of harmonic close-to-convex (resp. fully starlike) functions involving Gaussian
hypergeometric functions. In addition, we present a convolution
characterization for a class of univalent harmonic functions discussed recently
by Mocanu, and later by Bshouty and Lyzzaik in 2010. Our approach provide
examples of harmonic polynomials that are close-to-convex and starlike,
respectively.
