Male Fertility Diet
In general the diet for a healthy father-to-be should be every bit as balanced, varied, and nutritious as the diet for mother-to-be.
Specifically, future dads should eat plenty of foods rich in vitamin C, get more zinc and increase intake of calcium, vitamin D, vitamin E and L-Arginine.
There are many contributors towards the improvement of male fertility (some work more effectively in combination with others):

Promoters of Fertility
Inhibitors of Fertility