What are the parallelogram and quadrilateral rules

There are six important properties of parallelograms to know:

Opposite sides are congruent (AB = DC). 
Opposite angels are congruent (D = B). 
Consecutive angles are supplementary (A + D = 180°). 
If one angle is right, then all angles are right. 
The diagonals of a parallelogram bisect each other. 
Each diagonal of a parallelogram separates it into two congruent triangles.