if your not wanting to start testing for ovulation you can try having sex every 2nd day from about day 10 of your cycle (day one = first day of red blood/start of period) and continue this until about day 20 of your cycle.
if your cycles are anywhere near the 'normal' 28 day cycles.
if your cycles are longer or irregular you can keep trying this method or look into charing with
fertility friend and taking your temperature each morning and testing using Ovulation preditor kits like
these ones but you can get them from alot of different places.
hope i help.
others will have some pointers too