Every other day's good but every third day's perfectly adequate in a normal fertile couple. Generally about 5 days before ovulation is a good time to be thinking about it and the egg then deteriorates pretty rapidly (within hours) after ovulation so probably a day afterwards.
But sex every couple of days throughout your cycle and enjoying the process is best. It's quite a pleasant way to procreate.
Every day should be fine as long as there are no sperm count issues. I think the NHS recommends every 2-3 days. Personally I try to do every day/every other day pre ov and for a day or two after and then whenever we feel like it during the 2ww.
It is more important pre-O rather than post-O as the little guys can live up there for a while (3-5 days depending on where you read it) but the egg dies pretty quickly after it is released. Good luck.