Here are some tips from FertilityFriend on the timing and frequency of sexual intercourse in promoting pregnancy. This is an update on what was generally recommended in the past, particularly regarding the frequency of intercourse.
The Fertile Window
Sperm may last up to 5 days in cervical fluid and the egg may last up to 1 day after ovulation -- but these are the extremes. Intercourse during the two days prior to ovulation and on the ovulation day is more likely to produce a pregnancy.
Your fertile window is made up of the days in your menstrual cycle when pregnancy is possible. The length of this fertile phase is determined by the maximum life span of your partner's sperm and your egg. Sperm can survive a maximum of five days in fertile cervical fluid and your ovum can survive for up to one day. Your theoretical fertile window is thus six days long, comprised of the five days before ovulation and the day of ovulation. You only have a chance to conceive when you have intercourse on these days. This means that pregnancy is technically possible from intercourse on any of these six days. The likelihood of actually becoming pregnant, however, is dramatically increased when you have intercourse in the three days immediately leading up to and including ovulation. This makes a practical fertile window of just three days.
Frequency of Intercourse --
In the past it was suggested that the male refrain from ejaculation for 3 days prior to intercourse, giving the sperm cells a chance to mature in the epididymis, and giving the semen volume and sperm count time to build. But, this is no longer thought to be true. Frequent intercourse during the fertile window produces a higher chance of pregnancy.
There has been some speculation that couples who are trying to conceive should reduce the frequency of sexual intercourse during the fertile window to increase sperm supply. This is not true for most couples. While couples with known male factor issues should consult their doctor for the best intercourse strategy, couples with normal fertility and no known sperm issues should not reduce the frequency of intercourse in the fertile window. Your probability of conception is increased when you have intercourse multiple times in your fertile window. While it is true that sperm concentrations decrease slightly with increasing intercourse frequency, frequent intercourse is still more likely to result in conception than infrequent intercourse for couples with no male factor fertility issues. Each additional act of intercourse within your fertile window increases your probability of conception for that cycle.