I never understood how to chart and all that which I never really tried. I just knew that I ovulated around the 14th day so I would have intercourse on the 10th, 12th & 14th day. I would always know by the cervical mucus. There will be a day where you feel as if you need to go wipe down there because you are discharging so much clear discharge..well, that is the day you are most fertile. Good luck
There are a few different ways to try and tell. You can chart your temperature from first thing in the morning - your 'basal body temperature' or BBT (if you do a search you'll find tons of info), or you can look at your cervical mucus. I forget what how it's supposed to change - from watery to egg white or thick... The website: fertilityfriend.com - has a ton of Q and A on both topics. Hope it helps!