In general, I have read that you should start ttc on cd10 (cd 1 being your first day of your af! - but this is based on a 28 day cycle!!!) and continue through to cd16.
Adjust these days according to how long your cycles are.
Try logging onto babymed.Com, you can click on "fertility calender", plug in your dayes and how long your cycle is, and a whole calender pops up just for you, telling you when your best days to conceive are, when your af should arrive and when you can start to take a hpt!!!! I have found this site very useful!
About 10-11 days after you start your period, you can also just ttc every 2nd day - this way you may as well have "fun" at it, and increase your chances of becoming pregnant!
Good luck - I hope this info will help you
baby dust your way!