Your pH needs to be 4 to 4.5. DH pH is crucial too, I think his semen pH needs to be 7 -7.5 but check that on the TTC Girl FAQ.
It seems to be very important, many women don't do enough to bring it down and get another boy, even with a great cut-off or true O +12. And some women who have multiple girls even try shettles on O day for a Boy and get a girl, and then the next time they areTTC they have found this site and check their pH to find it's around the 4.5 mark.
The prep you put in now is well well worth it.
For things to eat / drink cranberry supps and crystal light are good for you and DH. But you need to do the girl diet for six weeks and the supps for that time too. Check out the TTC Girl FAQ, and make it your dietary bible for the forseeable!!!
Also check out the TTC Girl Spreadsheets for previous actual attempts, the boy ones greatly helped me.
GL ( all the above info can be found at the top of the gender Selection Forum)