It may likewise help to bring the legs close to the abdomen to facilitate pooling of sperm near the cervix. The sperm takes only minutes to travel from the cervix to the fallopian tubes, and can persist in there for as long as several days. This is the reason why the fertile window begins as early as five days prior to ovulation.
My recommendation for couples starting out is to make conception as stress-free and intervention-free as possible. Infertility is medically defined as the inability to conceive after 12 months of regular unprotected intercourse, or six months for women at or over the age of 35.
The concept is that infertility is not defined as specifically timed intercourse, with the understanding that every month may not be optimal in terms of the timing or other factors, but over several months there should be sufficient good chances to permit conception. Patients who do not conceive within this time frame, or those with identified risk factors, should consider getting an evaluation.