You can use ovulation predictor kits similar to pregnancy tests - you test them with wee once a day and they show you when your hormone level indicates you may be ovulating. They might take a month or two to get used to, but you can get them quite cheap on amazon. I used easy@home brand and they worked well.
You can also use a thermometer to test your temperature every morning which will confirm when ovulation has taken place. You need a thermometer which has 2 decimal places to be accurate - search BBT thermometer to get the right one.
To be 100% sure of ovulation I would use ovulation strips and BBT together, depending on how serious you are about trying - we wanted to maximise our chances every month so I did as much as I could!