Trying to conceive for a second

Ang

We're starting to try again for our second next month. We have a son who is 3.5. I'm older, 39 turning 40 this year so this is my last. We really would love a girl, but obviously we'll be happy with a happy healthy baby and healthy delivery. Anyone try for a girl and found out they were having a girl? Any tips? I know have sex days before you ovulate but anything else I should pay attention to?