When should you have sex if we are trying to get pregnant? The best way to try is to have sex two or three times a week after the period has finished. Sperm can live for a few days in the fallopian tubes so having sex every few days will make sure that the sperm will be there and ready to try and fertilise an egg.
If you are trying to precisely time love making then you should start trying several days before the expected day of ovulation. Ovulation occurs 14 days before a period starts. So if a woman has a regular cycle -say every 30 days- then she will ovulated 30 days minus 14 days so on day 16. If a couple were trying to maximise their love life around ovulation then I would suggest that they start actively trying from day 11 or 12 onwards (if her cycle is 30 days). If a woman has a 28 days cycle then active trying from day 9 or 10 would be ideal.
As a whole I am not a fan of fertility / ovulation meters. They can be useful in helping you identify when you might be ovulating and can be helpful when used in conjunction with fertility treatment. However for many couples they can cause a great deal of stress and unnecessary pressure in relationships- if you are trying to get pregnancy it is stressful enough without adding extra pressure. So if your cycle is regular then they are not really that necessary.