You can use an online ovulation calculator to find out when your most fertile time of the month is. Simply input the required details and the calculator will do the rest. It would be wise to use this ovulation calculator in conjunction with other methods to monitor your fertility such as temperatures and ovulation tests.
When an egg has matured the LH levels will rise causing the egg to exit the ovary and enter the fallopian tube (This is the part of your cycle that is known as ovulation). OPK’s are also known Ovulation predictor look very similar to pregnancy tests but work by measuring the SURGE of Luteinizing Hormone (LH) in your urine. By doing regular tests on the run up to your approx ovulation date you can get a much more accurate reading, Please remember that an unfertilised egg only has a time frame of around 24 hours before its too late! which is why some couples are left wondering why they have not fallen pregnant when they have had endless amounts of sex during the month but failed to have sex around the time of ovulation!
Ovulation tests can be purchased from local supermarkets and even on ebay and Amazon! In fact they are much cheaper on when you buy from ebay or Amazon: