Ovulation occurs approximately two weeks before the first day of your period. A woman who has menses every 28 days will ovulate on the 14th day of her cycle. A woman who has periods every 32 days will ovulate on the 18th day of her cycle. Since the day you ovulate might change, it helps if you have sex from a week before to a week after the expected day of ovulation. Timing sex with the date of ovulation can be sometimes stressful and having regular intercourse throughout the month is desirable.
Having sex every two to three days is optimal if you are trying for a pregnancy. Avoiding sex for a long period can decrease the sperm quality.
Sperm from semen released into the vagina reaches the fallopian tubes within minutes regardless of position during sex. There is no evidence that sexual position, orgasm or lying down for a prolonged period increases the chance of becoming pregnant. Avoid lubricants during sex as it might damage sperms.
A man who is obese, who smokes and drinks excessively is less likely to father a child. Maintaining a normal body weight, smoking cessation and reducing alcohol intake will help. A diet rich in anti-oxidants (fresh fruits and vegetables) or taking a multivitamin will help improve sperm quality. There is some evidence that using tight underwear and using laptops on your lap for long periods might worsen sperm quality.