You can start as soon as your child is born in trying to encourage his natural tendencies towards being gay. Give your child a good gay name, like Michael, Percival, or Algernon. People tend to treat people in a fashion similar to the way they have treated others with the same name, so a sort of conditioning results.
Freud's suggestion to mothers who want to raise their sons to be gay is to have a close, almost smothering relationship with their male offspring. Bad news for fathers is that they have to try to be distant and uninvolved.
Try to encourage your son to play with dolls and dress in women's clothes, as these sissified behaviors are highly correlated with adult homosexuality.
Of course there is the matter of a genetic component. It is thought that the genetics are carried on the X chromosome, thus coming from the mother's side (yes, there is scientific backing to the old joke "my mother made me a homosexual" - "Oh really? If I give her the yarn, can she make me one too?")
So, a man desiring a gay boy (as a son, not a sex partner, silly) should procreate with a woman who has maternal uncles, brothers, or even a father, who have successfully expressed a homosexual gene. Imagine the possibilities of one offspring of a mommy whose father and maternal grandfather were bother homosexuals.
Genetic reverie aside, let us examine the nurture component of the equation.
So far, the obvious has been stated -- fathers keep distance, or better yet single mother, though there have been plenty of families with a mother raising a son alone who turned out tragically to be straight.
But more intensive training is required. You should start your son on gogo dancing lessons as soon as he is able to walk. Dancing on a bar may be a future lucrative career.
Get your son to work on redecorating your home. Perhaps you could get your child a gay big brother from a volunteer organization to provide a masculine (or femme as the case may be) influence. If he can't have father, at least he can have a daddy.
Order your child clothing from the International Male tot's catalog. Yes, it's really true; you can buy hideous spandex workout items in child sizes.
A lifetime subscription to the Advocate can never begin too early in life. Indoctrinate your boy with the seeds of gay consumerism and start him on the right foot.
Make sure his toybox contains not only Lego and dollies but also toys made of latex and rubber. The child with the well-stocked toychest always will find friends eager to play.
Of course, even though you want your child to turn out gay, you must never let on that you actually approve of homosexuality. You need to instill a certain amount of self-loathing for your child to be a normal, twisted homosexual. The lure of the forbidden will draw your son to homosexuality. As you leave dolls and other sissy toys available, you must also tease and treat with contempt these girlish pursuits. Try to balance these things and your son should grow up as neurotic as homosexuals whose parents haven't made the special efforts to make them so that you have.
A father who wants to take a more active role can ridicule his son, speaking to him in a falsetto voice, imitating his feminine mannerisms, favoring a sibling who pursues more masculine activities, and any other humiliating ploys that come to mind. At the same time, a father should take opportunities to display himself in the nude, so as to stimulate his son's fantasy life, and create an equation of masculinity with unattainability. If this is done properly, this will produce a delightfully warped homosexual personality, nearly devoid of the potential for happiness and fulfillment. He will continually seek out men who are unavailable, drawn to their rugged masculinity and abusive tendencies.
Even if your child grows up and appears to be straight, even if he gets married, do not despair. It may be that he is actually a closeted homosexual seeking furtive pleasure with his own kind covertly, while attempting to maintain a facade of normalcy. You will know that he's really just a big mama's boy faggot.