Hi I read this somewhere and I hope these informations are helpful!
1) sperm containing Y chromosomes (boys) move faster than X(girls) chromosome carrying sperm. For this reason, couples who wants to conceive a boy have intercourse no more than 24 hours before ovulation to no more than 12 hours past ovulation.
2) Deep penetration from your partner will deposit sperm closer to the cervix, allowing the more aggressive Y sperm to get a head start in fertilization.
3) Evening Primrose Oil supplements are thought to help women conceive sons by increasing the production of higher quality cervical mucus. Many women also believe taking Guaifenesin tablets during the five days before ovulation will help thin out cervical mucus that is too thick, thus improving the odds of conceiving a son. Potassium supplements are also sometimes said to benefit women who are trying to have boys.
It’s strongly recommended that you discuss your plan with your health-care provider. Many over-the-counter supplements can cause unintended side effects or interactions with other prescription medications.
Change your diet to include lots of red meat, salty snacks, and cola soft drinks.
Let your partner initiate sex and focus on his pleasure. If the man climaxes first, you’ll conceive a baby boy.
Schedule your lovemaking sessions for odd numbered days of the month.
Have sex at night, preferably when there’s a quarter moon in the sky.
Have as much sex as possible, since many people believe more boys are conceived during the “honeymoon” phase of a relationship.
Have the man drink coffee before sex, since this causes the sperm with Y chromosomes to become more active.
http://pregnancy.lovetoknow.com/wiki/How_to_Conceive_a_Boy