tax and married file separately

Hi:

We married and have a baby and a house (we live in the same house). How should we file the tax separately?
$5000 child care exemption is deducted from my w2 already. How do we share that $5000? My baby should be who's dependent? How do we separate the mortgage interest and property tax? Is there any role that we can apply?

I assume that we can't take those deductions on both sides.

thanks