Wife & I discussed this after our first (boy), we wanted a 2nd boy - we decided to just stick to the Shettles method... IDK if I was supposed to have boys or it really works, but we had another boy.
If you want another girl, doesn't seem like you have to change much, but if you want a boy, here are my tips:
Timing; close to ovulation
Position; doggy, deep penetration
Climax; partner needs an orgasm before you (preferably multiple)
Drink a few cups of coffee 30-45 minutes before doing the deed