Some basic principles from the Compendium of the Catechism (337-338):
Natural Family Planning (NFP) methods provide married couples with the means of achieving or avoiding pregnancy based on natural signs of fertility, in a manner that is environmentally safe, respectful of the bodily integrity of spouses, and compatible with Catholic moral teaching and the dignity of the human person.
Here are two helpful groups that assist couples in living out the call to marriage and sexuality that is free, faithful, total and forever:
There are a few key N.F.P. methods to choose from; please feel free to research them starting with the links below and find what works best for you and your family.