There are probably some set rules to break this down, but look at it this way: there are only 4 possibilities that you need to check.

1) A and B are disjoint.

2) A and B intersect, but do not contain one or the other.

3) A is a subset of B.

4) B is a subset of A.

(I suppose you ought to include the possibilities were either A or B or both are the empty set, but these should be easy.)

-Dan