Work on shading and tonal variates throughout. For the first one, the face needs to look more realistic - the idea of it is sweet though. The second one is good but just make sure its really clear, like the lines and shape of the figure. For the third one, it needs to look more believable. The golf club looks awkward, and if it already smashed through the cups it should be in front of them, not behind still. Also try working into the negative space of the background to make it part of the drawing.