Do you know:
sperm travels 3mm per minute (according to current scientific research), it takes on average 10 hours to reach the egg (discovery channel) and it can stay alive 48-72 hours (even longer in a favourable enviroment or when you are lucky to have some super sperms)
egg is released approx 24 hours after the LH surge. it stays alive for 12-24 hours.
when the sperms reach the fallopian tube and the egg isn't there yet, they kind of go into the waiting bay. They don't wait in an orderly manner though. They will bounce off each other while waiting for the egg to come. After all surprise surprise, there is no opposite attracts / magnetic reaction between egg and sperms, it is purely the bumping that gets the sperm inside the egg.
the boy sperms are more robust, they bump hard and get spent sooner while the girls have the stamina.
it takes about 200 sperms to bump and eventually crack the egg shell, and only the 1st lucky sperm that gets through the crack fertilizes the egg.
once fertilized it takes just over a week for the egg to travel down the tube and implant in the lining of uterus. the implantation usually happens around 9DPO.
about gender selection:
styles recommended: the doggie style provides shortest distance for sperm to travel, good for conceiving boys. the missionary style keeps the sperm furthest away from the egg, good for conceiving girls.
the popular Shettles Method says to conceive a girl you need to intercourse 2-3 days prior to ovulation, then no sex till the egg is gone. it takes that long to tire the boy sperms out and hopefully when ovulation occurs, there are only girl sperms left to do the job. And to conceive a boy, you need to intercourse on the day of ovulation. the boy sperms are sure to beat the girl sperms in the race to the egg.
the O+12 method, I only heard it the first time today. it suggests to have sex 12 hours after ovulation will increase the chance of having a girl. I am not sure about this one. waiting for 12 hours doesn't make the girl sperms swim faster, it only gives you an ageing egg.
That said, you have to be in it to win it. After all if you do try, you always have 50/50 chance to get it right, Right?