Important: Please note that this is just a very rough guideline. To determine the best days to conceive and to get accurate timings, use an Ovulation Test.
Disclaimer: Making love on your most fertile days does not necessarily mean that you will conceive. Your ability to conceive is dependent on other factors as well. These days are meant to be a rough guide only.
How do ovulation test kits work?
Ovulation tests help you identify the two days of the month when you're most likely to get pregnant. There are changes in your body right before an egg is released from the ovary (ovulation). Ovulation tests work by detecting one of these changes, specifically the increase of luteinizing hormone (LH) levels in urine. The LH surge, as it is commonly called, precedes ovulation by 24 to 36 hours. Predicting your LH surge with an ovulation test enables you to identify the most fertile time of your cycle - the two days beginning with your surge. Ovulation tests can be over 99% accurate (in laboratory testing) in detecting your LH surge.
You can maximize your chances of becoming pregnant if you have intercourse within 24 to 36 hours after detecting your LH surge. Timing is one of the most important factors when you're trying to get pregnant.
Source: First Response