you could check out chinese gender calender and see how you went for your last children.. For my it was 100% ( 1 x boy 1 x girl for me) .. i think it is just a fluke.. but who knows!

I dont think there is any certain method, you could seach for billings method? I have also read somewhere about diet being a factor... but who knows. all the best in achieving a healthy baby

xoxox