The biggest problem is that people wait til day 13-14 of their cycle when they should be bd'ing from day 7.
I just wanted to comment that this is not really correct as it really depends on how long your cycle is. I usually ovulate around CD18, so doing it from day 7 is not needed and days 13/14 onwards would actually be the right time for me.
to the original poster: ive always been wondering this! Ive been using the sperm meets egg plan which has you bding every other day then 3 days in a row once you get the positive ov test. when i met with my fertility specialist she said every other day is fine and if i did CD15, 17, 19 I would cover all bases. but this month we ended up doing it everyday around that time as I never got a positive ov so I was nervous