The ideal time for conception is 14 days before expected date of comming menses.
If periods are not regular you can judge it by decend in woman's basal body temreture.OR by ovulation predictor test(LH surge test) Ovulation is within 24 to 48 hrs of surge test +ve. try from the day of +ve test for 5 days.
A woman should in a happy &+ve mood before sex
She should lie on apillow raising her buttocks for half hr. after sex.
Both the partners should take Tab Folic acid
(5mg. once aday),cap. of vit E (500mg. once a day) For Good fertilisation .