Charting is very useful, all you need is a thermometer to take your temperature every morning when you wake up. You keep the data (most of us we use fertility friend https://www.fertilityfriend.com/) and if you like you take notes on your cervical mucus too, egg white is the most fertile. This way you can pin point your ovulation day, which is the day an egg can be fertilised. The goal is to have sex the days before ovulation and the ovulation day of course.