For a BOY ...
Okay, ready?? :LOL
Here we go:
There are many, many ways to influence gender. Shettle's method, for me, did not work. We have three (DH has another, too) girls.
We Shettled for a boy with the last baby and nada.
Shettles, to have a boy, is to baby dance as close to ovulation as possible - post-ovulation, that is. The idea is that the swimmers who are male are stronger and faster and if the egg has already been released, the male spermies will fertilize before the females make it up there. If you BD too early, the egg will not yet be out and when it is released the male sperm will already have died (not being hardy or living as long as the females) and the females will be all that is left to fertilize the egg.
There are other ideas as well. (I am a member of a gender determination group). There is the "boy diet" (and the girl diet). For the boy diet, the studies showed diets high in sodium and potassium led to a higher instance of male conceptions. Some say it changes the polarization of the egg. This I haven't tried, but will the two months before we TTC. Potatoes, avocados, and bananas are all high in potassium. Some take it really far and end up eating NOTHING with calcium or magnesium because it is on the "girl" diet. Not sure that's a great idea, but hey - to each his own.
There is also the idea of environment. This is the vaginal walls, essentially. Because an acidic environment is going to be hostile to sperm, it will kill off the male swimmers who lead, leaving only the females. Those of us with lots of girls are believers that if you douche (gently - or drip a few drops) of baking soda water just before baby dancing, it will make the environment more basic and thus receptive to the male spermies.
You can also alter your body chemistry by diet, and I've heard of moms taking Alka Seltzer an hour or so before BDing to change the pH. You can get pH strips from a pool supply company or school supply place (for science projects). Aside from checking pH of your vaginal walls, some check cervical pH and saliva.
I've checked my vaginal pH and it is VERY acidic, so there may be some truth to that.
DH drinking caffeine before BDing is also said to help, as is abstinence for two days before, I believe.