There are a number of popular ways to predict when you’re ovulating and maximise your chances of conceiving a boy. These include:

Ovulation calendar -
You can use an ovulation calendar to predict ovulation if you have regular periods.

Basal Thermometer -
You can use a basal thermometer to detect the small temperate increase which happens when a woman releases an egg. The egg release stimulates the production of progesterone, which raises body temperature. This method does not actually predict the time of ovulation, but does show that you’ve actually ovulated.

Ovulation tests or ovulation kits -
Ovulation tests work by detecting an LH-surge in the body, which happens just before ovulation occurs. These tests are without doubt the easiest and most accurate way to predict ovulation, and are cheaply available in chemists / pharmacies or online.

For the highest degree of accuracy, therefore, How to Conceive a Boy recommends that you use an ovulation test to predict ovulation.