How can I increase my cat's appetite?

my cat is one, and he seems to have little interest in food. He is very skinny and i want him to start eating more, but it takes him a whole day to finish half a can of wet food (and he's very particular, the wet food has to be sliced or in chunks otherwise he won't eat it). He eats dry food, but i was wondering if there is a way to increase his appetite so he can start eating more. please help, I don't want my cat to look like he's on the brink of starvation!